`const` support

[snowsignal]

Closes #44.

This PR will allow the typeshare annotation to be used for const variables. This will copy the variable declaration into the output for the respective language.

For example:

const ANSWER_TO_EVERYTHING: u32 = 42;
const BEST_FILM: &str = "The Tree of Life";

This would become:

const ANSWER_TO_EVERYTHING = 42;
const BEST_FILM = "The Tree of Life";

class Constants {
  static let ANSWER_TO_EVERYTHING = 42
  static let BEST_FILM = "The Tree of Life"
}

const val ANSWER_TO_EVERYTHING = 42
const val BEST_FILM = "The Tree of Life"

const ANSWER_TO_EVERYTHING = 42
const BEST_FILM = "The Tree of LIfe"

As of right now, this PR only supports integers, floats, and strings as constant types.

[beyera]

I would like to have this 👍

[lpi]

Is this still being worked on? It seems very useful

[snowsignal]

Is this still being worked on? It seems very useful

Sorry, this has been put on hold for a while. I'm no longer actively involved with this specific project but I'll try to get this merged when I can.