chore: combine markdown and JS linting, and include .mjs support

- Removed unused "lint:js" script and merged it into "lint"
- Updated ESLint command to include .js, .jsx, and .mjs extensions

Author: prateekbisht23

package.json

@@ -7,8 +7,7 @@
     "postinstall": "rm -rf node_modules/markdownlint-cli/node_modules/markdownlint",
     "install:config": "cd packages/eslint-config-airbnb && npm prune && npm install",
     "install:config:base": "cd packages/eslint-config-airbnb-base && npm prune && npm install",
-    "lint": "markdownlint --config linters/.markdownlint.json README.md */README.md",
-    "lint:js": "eslint -c linters/.eslintrc . --ext .js --ext .jsx",
+    "lint": "markdownlint --config linters/.markdownlint.json README.md */README.md && eslint -c linters/.eslintrc . --ext .js --ext .jsx --ext .mjs",
     "pretest": "npm run --silent lint",
     "test": "npm run --silent test:config && npm run --silent test:config:base",
     "test:config": "cd packages/eslint-config-airbnb; npm test",

packages/eslint-config-airbnb-base/README.md

@@ -62,12 +62,12 @@ Our default export contains all of our ESLint rules, including ECMAScript 6+. It
 
 2. Add `"extends": "airbnb-base"` to your .eslintrc.
 
-⚠️ **Note**: ESLint only lints `.js` files by default.  
+> **Note**: ESLint only lints `.js` files by default.  
   
   If your project uses `.jsx` (or `.tsx` with TypeScript), you need to pass extensions to the CLI:  
 
   ```sh
-  eslint . --ext .js,.jsx
+  eslint . --ext .js, .jsx, .mjs
   ```
 
   Without this, JSX-related rules will not apply to `.jsx` files.

packages/eslint-config-airbnb/README.md

@@ -58,11 +58,11 @@ If you don't need React, see [eslint-config-airbnb-base](https://npmjs.com/eslin
 
 2. Add `"extends": "airbnb"` to your `.eslintrc`
 
-⚠️ **Note**: ESLint only lints `.js` files by default.  
+> **Note**: ESLint only lints `.js` files by default.  
   If your project uses `.jsx` (or `.tsx` with TypeScript), you need to pass extensions to the CLI:  
 
   ```sh
-  eslint . --ext .js,.jsx
+  eslint . --ext .js, .jsx, .mjs
   ```
 
   Without this, JSX-related rules will not apply to `.jsx` files.