More ``vim`` plugins

[Mischback]

• gitgutter: indicate changes based on git
  • https://vimawesome.com/plugin/vim-gitgutter
  • https://github.com/airblade/vim-gitgutter
• indent-guides: indicate indents
  • https://vimawesome.com/plugin/indent-guides
• https://github.com/hail2u/vim-css3-syntax
• https://github.com/ap/vim-css-color

Reference

• For development of CSS-specific syntax stuff, this might be a nice reference: Inconsistent CSS property name color NLKNguyen/papercolor-theme#170