Add eslint-plugin-eslint-plugin

[bmish]

1. Enforces the recommended practices for eslint rules and rule tests using eslint-plugin-eslint-plugin which is commonly used internally by eslint plugins.
2. Disables eslint-plugin/require-meta-type which can be addressed as a follow-up.
3. Exports rules using export default instead of module.exports =. Why?
   • This is needed so that eslint-plugin-eslint-plugin will recognize the rules since export default is expected in files that use sourceType: module.
   • For module files (which import statements instead of require), we might as well use export statements instead of module.exports too to adopt fully modern syntax.

[ljharb]

There’s no need to make eslintrc valid json; trailing commas and comments are a good feature.

[bmish]

There’s no need to make eslintrc valid json; trailing commas and comments are a good feature.

I agree those are good features. It's just a bit inconvenient to use those in JSON files since some IDEs will show syntax warnings.

It's also confusing that the .eslintrc in this project has a mixture of single quotes, double quotes, and no quotes surrounding property names, so it's very difficult to tell what style to follow.

That's why I normally use the JS format of the config file .eslintrc.js so I can just let prettier handle this for me.

Anyways, I reverted the changes to the original lines in .eslintrc.

[codecov]

Codecov Report

Merging #818 (94a4684) into master (f44fc05) will not change coverage.
The diff coverage is n/a.

❗ Current head 94a4684 differs from pull request most recent head f1414cf. Consider uploading reports for the commit f1414cf to get more accurate results

@@           Coverage Diff           @@
##           master     #818   +/-   ##
=======================================
  Coverage   99.22%   99.22%           
=======================================
  Files          98       98           
  Lines        1417     1417           
  Branches      477      477           
=======================================
  Hits         1406     1406           
  Misses         11       11           

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[ljharb]

Thanks!