Enable the import/no-commonjs ESLint plugin rule

Given the amount of work put into removing `require`-calls from the code-base, let's ensure that new ones aren't accidentally added in the future.

Note that we still have a couple of files where `require` is being used, in particular:
 - The Node.js examples, however those will be updated to use `import` in PR 17081.
 - The Webpack examples, and related support files, however I unfortunately don't know enough about Webpack to be able to update those. (Hopefully users of that code will help out here, once version `4` is released.)
 - The `statcmp`-tool, since *some* of those `require`-calls cannot be converted to `import` without other code changes (and that file is only used during benchmarking).

Please find additional details at https://github.com/import-js/eslint-plugin-import/blob/main/docs/rules/no-commonjs.md

.eslintrc

@@ -39,6 +39,7 @@
     "import/named": "error",
     "import/no-cycle": "error",
     "import/no-empty-named-blocks": "error",
+    "import/no-commonjs": "error",
     "import/no-mutable-exports": "error",
     "import/no-self-import": "error",
     "import/no-unresolved": ["error", {