Proposal - introduce language tags

[dkuku]

Currently hex supports multiple languages that may require additional dependencies and setup that we may not wan't to include.
Examples:

• I'm searching for elixir package and I want to skip gleam packages.
• I'm using nerves and I don't have c and rust toolchain installed so I wan't to see if a package that I found is a nif - the description is not always clear.
• I'm searching for rustler package examples.
  Some of this metadata can be probably extracted from deps. I see that we show dependents so this data is already present.
  Packages that depend on rustler or rustler precompiled could be marked as such.

[dkuku]

I see similar proposal was here it was about search so I did not checked it before, I searched for tags and icons.