Add typecheck step to CI (#685)

Add a "typecheck" script (tsc --noEmit) to package.json and run it
in CI before lint and test. This catches TypeScript type errors that
esbuild silently ignores during bundling.

Co-authored-by: Thomas Ruggeri <truggeri@github.com>

Author: jeffwidman

.github/workflows/ci.yml

@@ -22,6 +22,8 @@ jobs:
 
     - run: npm ci
 
+    - run: npm run typecheck
+
     - run: npm run lint
 
     - run: npm test

package.json

@@ -5,6 +5,7 @@
   "main": "dist/index.js",
   "scripts": {
     "build": "esbuild src/main.ts --bundle --platform=node --target=node24 --outfile=dist/index.js --format=cjs --legal-comments=none",
+    "typecheck": "tsc --noEmit",
     "lint": "eslint . --ext .ts",
     "test": "jest",
     "dry-run": "esbuild src/dry-run.ts --bundle --platform=node --target=node24 --format=cjs --outfile=dist/dry-run.js --log-level=warning && node dist/dry-run.js"