Add `remote_theme` configuration to documentation

Change number of skins to 9

Update installation documentation

Include new `jekyll-remote-theme` method for using Ruby gem version of the theme with GitHub Pages hosted sites.

ref: https://github.com/mmistakes/minimal-mistakes/issues/1339

Update CHANGELOG and history

Release 4.7.0 :gem:

Update skin count

Add plum skin to README

Add plum skin

Add placeholder to table

Update CHANGELOG and history

no message (#1319)

Update README

Update CHANGELOG, history, and README

Add neon skin

Update CHANGELOG and history

Update jekyll-toc with heading classes fix (#1337)

Update CHANGELOG and history

Aqua skin (#1336)

* Add new skin and update docs

* Better screenshots for aqua skin

Update CHANGELOG and history

Fix author profile link texts (#1328)