- Updates nodemon scripts to watch specific directories instead of ignoring several
- Split watch tasks for CSS and JS into main and docs
- Add docs-watch script to serve the docs instead of just build
- Add new start script so that instead of two tabs, one for docs-watch and one for watch, we just run npm start

With the current docs directory setup, I'm making too many mistakes and have to manually address path changes and directory moves on deploy. This makes for a frustrating experience developing locally and shipping releases. With this PR, we're basically back to the same setup from v3—duplicating the dist directory into our docs directory. Not the most ideal, but very straightforward for me as the release manager.

Only bundlesize is kept back for Node.js 10.x compatibility.

I was getting port in use errors.

Newer bundlesize versions still don't work with node.js 10.x.

babel has some bugs that we need to be fixed.

Downgrade bundlesize until they make brotli optional since it doesn't work with node.js 10.x yet.

So, babel, qunit/karma-qunit and bundle-size aren't the latest versions.

* update docs path from docs/4.0/ to docs/4.1/

* bump version to 4.1.0

* Update redirects to work for 4.1 docs move

* Update docs version switcher to include latest and link to 4.0 docs

* re-run dist

* Update package-lock.json

* Update docs-navbar.html

Kept back karma-qunit and qunitjs because tests fail.

Also, refactor ESLint and stylelint config files; now everything will work from our root dir.

Update our browserslist.

* Add `last 1 major version` and `>= 1%`.
* Add Firefox.

Firefox v38 is older than the ESR, so basically replace ESR with v38.