Add Elixir syntax styles

[BadBastion]

Description of the Change

Improved Elixir syntax highlighting

• Operators and structure (tuples, arrays...) now dimmed(@mono-2)
  • The heavy use operators in elixir combined with the fact that functions can have special characters such as .empty? or special meaning such as ^pinned means that using different colors for operators and functions improves readability a bit.
• Atoms (& functions) now have their own color (@oc-blue-3)
• Strings/charlists/regex now have their own color (@oc-pink-4)
• Strings/charlists/regex have normal highlighting inside interpolation (basically a bugfix)
• Improved consistency of module highlighting (@oc-orange-4)
  • Module names don't always have the same color depending on the context. Module Definitions are orange while import and usage are yellow. This is fixed by making all instances of modules orange.
• Changed color of importing functions to match module attributes (@oc-yellow-3)
  • Importing functions such as [use, require, import, alias] are most often placed alongside module attributes at the start of modules/functions. They both serve in a general sense as elixir's tools setup for module/function (constants, docs, imports, alias, and so on) so might as well have consistent coloring.

Issues

@import 'syntax/elixir'; seems to be throwing errors (file not found). Changing this to styles/syntax/elixir fixes the problem, but isn't consistant with the other imports in index.less.

[BadBastion]

Great syntax by the way! I personally have been using this lately and liking it a lot.

[pfist]

Thanks for the contribution! It looks great. 😄

Are you still having issues with the import statement? I tried testing your changes locally with @import syntax/elixir and didn't get any errors.

[BadBastion]

@nkpfstr I tested it on another computer and it was fine. My laptop's hard drive recently started dying so I have a feeling it was related to that and not the code. Sorry for the false alarm :P

[pfist]

No worries! Would you prefer to update your PR or let me merge it then update the import myself? Obviously the latter would be less work for you, but I thought I'd ask. 😃

[BadBastion]

Fixed, and ready to pull

[pfist]

Great! Thanks again. I'll merge it now and publish it on apm tomorrow morning. ^^