feat: switched ESLint config from JS to TS (#2351)

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## PR Checklist

- [x] Addresses an existing open issue: fixes #000
- [x] That issue was marked as [`status: accepting
prs`](https://github.com/JoshuaKGoldberg/create-typescript-app/issues?q=is%3Aopen+is%3Aissue+label%3A%22status%3A+accepting+prs%22)
- [x] Steps in
[CONTRIBUTING.md](https://github.com/JoshuaKGoldberg/create-typescript-app/blob/main/.github/CONTRIBUTING.md)
were taken

## Overview

Switches the file formats from `.mjs` & `.js` to `.mts` and `.ts`.

🎁

Author: JoshuaKGoldberg

eslint.config.js eslint.config.tseslint.config.js renamed to eslint.config.ts

@@ -113,7 +113,7 @@ describe("blockESLint", () => {
 			    },
 			  ],
 			  "files": {
-			    "eslint.config.js": "import eslint from "@eslint/js";
+			    "eslint.config.ts": "import eslint from "@eslint/js";
 			import { defineConfig, globalIgnores } from "eslint/config";
 			import tseslint from "typescript-eslint";
 
@@ -267,7 +267,7 @@ describe("blockESLint", () => {
 			    },
 			  ],
 			  "files": {
-			    "eslint.config.js": "import eslint from "@eslint/js";
+			    "eslint.config.ts": "import eslint from "@eslint/js";
 			import { defineConfig, globalIgnores } from "eslint/config";
 			import tseslint from "typescript-eslint";
 
@@ -424,7 +424,7 @@ describe("blockESLint", () => {
 			    },
 			  ],
 			  "files": {
-			    "eslint.config.mjs": "import eslint from "@eslint/js";
+			    "eslint.config.mts": "import eslint from "@eslint/js";
 			import { defineConfig, globalIgnores } from "eslint/config";
 			import tseslint from "typescript-eslint";
 
@@ -584,7 +584,7 @@ describe("blockESLint", () => {
 			    },
 			  ],
 			  "files": {
-			    "eslint.config.js": "/*
+			    "eslint.config.ts": "/*
 			This is a great config!
 			*/
 			/*
@@ -752,7 +752,7 @@ describe("blockESLint", () => {
 			    },
 			  ],
 			  "files": {
-			    "eslint.config.js": "import eslint from "@eslint/js";
+			    "eslint.config.ts": "import eslint from "@eslint/js";
 			import { defineConfig, globalIgnores } from "eslint/config";
 			import tseslint from "typescript-eslint";
 
@@ -899,7 +899,7 @@ describe("blockESLint", () => {
 			    },
 			  ],
 			  "files": {
-			    "eslint.config.js": "import eslint from "@eslint/js";
+			    "eslint.config.ts": "import eslint from "@eslint/js";
 			import { defineConfig, globalIgnores } from "eslint/config";
 			import tseslint from "typescript-eslint";
 
@@ -1059,7 +1059,7 @@ describe("blockESLint", () => {
 			    },
 			  ],
 			  "files": {
-			    "eslint.config.js": "import eslint from "@eslint/js";
+			    "eslint.config.ts": "import eslint from "@eslint/js";
 			import { defineConfig, globalIgnores } from "eslint/config";
 			import tseslint from "typescript-eslint";
 
@@ -1207,7 +1207,7 @@ describe("blockESLint", () => {
 			    },
 			  ],
 			  "files": {
-			    "eslint.config.js": "import eslint from "@eslint/js";
+			    "eslint.config.ts": "import eslint from "@eslint/js";
 			import { defineConfig, globalIgnores } from "eslint/config";
 			import tseslint from "typescript-eslint";
 
@@ -1333,7 +1333,7 @@ describe("blockESLint", () => {
 			    },
 			  ],
 			  "files": {
-			    "eslint.config.js": "import eslint from "@eslint/js";
+			    "eslint.config.ts": "import eslint from "@eslint/js";
 			import { defineConfig, globalIgnores } from "eslint/config";
 			import tseslint from "typescript-eslint";
 
@@ -1459,7 +1459,7 @@ describe("blockESLint", () => {
 			    },
 			  ],
 			  "files": {
-			    "eslint.config.js": "import eslint from "@eslint/js";
+			    "eslint.config.ts": "import eslint from "@eslint/js";
 			import { defineConfig, globalIgnores } from "eslint/config";
 			import tseslint from "typescript-eslint";
 
@@ -1582,7 +1582,7 @@ describe("blockESLint", () => {
 			    },
 			  ],
 			  "files": {
-			    "eslint.config.mjs": "import eslint from "@eslint/js";
+			    "eslint.config.mts": "import eslint from "@eslint/js";
 			import { defineConfig, globalIgnores } from "eslint/config";
 			import tseslint from "typescript-eslint";
 
@@ -1705,7 +1705,7 @@ describe("blockESLint", () => {
 			    },
 			  ],
 			  "files": {
-			    "eslint.config.js": "import eslint from "@eslint/js";
+			    "eslint.config.ts": "import eslint from "@eslint/js";
 			import { defineConfig, globalIgnores } from "eslint/config";
 			import tseslint from "typescript-eslint";
 
@@ -1736,25 +1736,25 @@ describe("blockESLint", () => {
 			expect(actual).toBeUndefined();
 		});
 
-		it("returns data when there is an eslint.config.js file", () => {
+		it("returns data when there is an eslint.config.ts file", () => {
 			const sourceText = "export default ...";
 
 			const actual = testIntake(blockESLint, {
 				files: {
-					"eslint.config.js": [sourceText],
+					"eslint.config.ts": [sourceText],
 				},
 			});
 
 			expect(mockBlockESLintIntake).toHaveBeenCalledWith(sourceText);
 			expect(actual).toBe(mockIntakeData);
 		});
 
-		it("returns data when there is an eslint.config.mjs file", () => {
+		it("returns data when there is an eslint.config.mts file", () => {
 			const sourceText = "export default ...";
 
 			const actual = testIntake(blockESLint, {
 				files: {
-					"eslint.config.mjs": [sourceText],
+					"eslint.config.mts": [sourceText],
 				},
 			});
 

src/blocks/blockESLint.test.ts

@@ -38,7 +38,12 @@ export const blockESLint = base.createBlock({
 	},
 	intake({ files }) {
 		const eslintConfigRaw = intakeFile(files, [
-			["eslint.config.js", "eslint.config.mjs"],
+			[
+				"eslint.config.ts",
+				"eslint.config.mts",
+				"eslint.config.js",
+				"eslint.config.mjs",
+			],
 		]);
 
 		return eslintConfigRaw ? blockESLintIntake(eslintConfigRaw[0]) : undefined;
@@ -47,7 +52,7 @@ export const blockESLint = base.createBlock({
 		const { explanations, extensions, ignores, imports } = addons;
 
 		const configFileName =
-			options.type === "commonjs" ? "eslint.config.mjs" : "eslint.config.js";
+			options.type === "commonjs" ? "eslint.config.mts" : "eslint.config.ts";
 
 		const explanation =
 			explanations.length > 0