chore: lint mjs files and ignore json files (#6352)

**What's the problem this PR addresses?**

`.mjs` files (`eslint.config.mjs`) aren't linted and in my IDE it keeps
breaking the JSON files.

**How did you fix it?**

Lint `.mjs` files and ignore JSON files.

**Checklist**
- [x] I have read the [Contributing
Guide](https://yarnpkg.com/advanced/contributing).
- [x] I have set the packages that need to be released for my changes to
be effective.
- [x] I will check that all automated PR checks pass before the PR gets
reviewed.

eslint.config.mjs

@@ -1,12 +1,15 @@
-import eslintConfig from '@yarnpkg/eslint-config';
 import reactEslintConfig from '@yarnpkg/eslint-config/react';
+import eslintConfig      from '@yarnpkg/eslint-config';
 
+// eslint-disable-next-line arca/no-default-export
 export default [
   ...eslintConfig,
   ...reactEslintConfig,
 
   {
     ignores: [
+      `*.json`,
+      `**/coverage/**`,
       `.yarn`,
 
       `packages/docusaurus/.docusaurus`,
@@ -32,7 +35,7 @@ export default [
 
       // Minimize the diff with upstream`,
       `packages/yarnpkg-pnp/sources/node`,
-      `packages/yarnpkg-pnp/sources/loader/node-options*`
+      `packages/yarnpkg-pnp/sources/loader/node-options*`,
     ],
   },
 

package.json

@@ -58,7 +58,7 @@
     "build:plugin-workspace-tools": "yarn node -r ./scripts/setup-ts-execution ./scripts/create-mock-plugin.ts workspace-tools",
     "build:plugin-commands": "node ./scripts/gen-plugin-commands.js > packages/yarnpkg-cli/sources/pluginCommands.ts",
     "build:compile": "rm -rf \"$0\"/lib && mkdir -p \"$0\"/lib && rsync -a --include '*.d.ts' --exclude '*.ts' --exclude '*.tsx' \"$0\"/sources/ \"$0\"/lib/ && node scripts/compile \"$@\"",
-    "test:lint": "eslint --max-warnings 0 \"./**/*.@(tsx|ts|js)\"",
+    "test:lint": "eslint --max-warnings 0 \"./**/*.@(tsx|ts|js|mjs)\"",
     "test:unit": "jest",
     "typecheck:all": "tsc -p ."
   },