Automatically create a tsconfig.json when entrypoint is TypeScript

docusaurus/docs/adding-typescript.md

@@ -11,7 +11,7 @@ To add TypeScript to a Create React App project, follow these steps:
 
 1. Run `npm install --save typescript @types/react @types/react-dom @types/jest` (or `yarn add typescript @types/react @types/react-dom @types/jest`).
 2. Rename the `.js` files you want to convert: use `.tsx` if they use JSX or `.ts` if not (e.g. `git mv src/index.js src/index.tsx`).
-3. Create a [`tsconfig.json` file](https://www.typescriptlang.org/docs/handbook/tsconfig-json.html) at the root directory with `{}` in it.
+3. Create a [`tsconfig.json` file](https://www.typescriptlang.org/docs/handbook/tsconfig-json.html) at the root directory with `{}` in it. Alternatively, rename `index.js` to `index.tsx`.
 4. Restart your development server (if applicable). This will set sensible defaults and the required values in your [`tsconfig.json` file](https://www.typescriptlang.org/docs/handbook/tsconfig-json.html).
 
 Type errors will show up in the same console as the build one.

packages/react-scripts/scripts/utils/verifyTypeScriptSetup.js

@@ -21,7 +21,10 @@ function writeJson(fileName, object) {
 
 function verifyTypeScriptSetup() {
   if (!fs.existsSync(paths.appTsConfig)) {
-    return;
+    if (!paths.appIndexJs.match(/\.ts?$/)) {
+      return;
+    }
+    writeJson(paths.appTsConfig, {});
   }
 
   const isYarn = fs.existsSync(paths.yarnLockFile);