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

external/dist/webpack.js

@@ -12,6 +12,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+/* eslint-disable import/no-commonjs */
 
 "use strict";