Learn TypeScript Linting updates

Per comments https://github.com/microsoft/TypeScript/issues/30553#issuecomment-500125274 & https://github.com/microsoft/TypeScript/issues/30553#issuecomment-500165271 some parts of configuring `typescript-eslint` were missed. The main two are:

`typescript-eslint/eslint-recommended` plugin 

and 

`"project": "./tsconfig.json"`
