feat(extensions): add explicit full 'mini.nvim' support

[echasnovski]

This PR adds full support for 'mini.nvim'. Addresses (part of) #81.

Already present 'mini.files' highlight groups are not changed. Of course, feel free to adjust the rest.

Some notes about highlighting decisions:

• Explicit links usually indicate that the highlight group is the same as 'mini.nvim' default. If :colorscheme cyberdream is the first and only call in user's config, they are, strictly speaking, not needed. However, they are present to ensure the calling :colorscheme cyberdream after some other color scheme (which might have overridden default highlight) results in the same highlighting.
• Colors for 'mini.statusline' modes are taken from Heirline highlight groups.
• Other stylistic choices are made the way I think is best here, which might not be fully in the spirit of the color scheme (again, feel free to manually adjust):
  • Using background highlighting for MiniDiffOverXxx):
  • Vibrant background highlighting in 'mini.hipatterns'.
  • Colorful highlighting of 'mini.jump2d' spots.
  • MiniTablineModifiedXxx being inverted MiniTablineXxx.

[scottmckendry]

Incredible! Thanks for working on this @echasnovski!
The only change I've made is to use the solid alternative for the bg color when blending on some of the groups. Probably another good reason to explicitly define these colors instead of dynamically generating them at runtime.