Write go to Definition

[kharus]

Probably requires both

• https://microsoft.github.io/language-server-protocol/specification#textDocument_definition
• https://microsoft.github.io/language-server-protocol/specification#textDocument_typeDefinition

[anka-213]

We can delay the typeDefinition thing if we want. That is less important

[anka-213]

I think the main component of this would be to add Identifier to the Ast and put location for itself and location for its definition in its annotation. The later thing would be a part of the type checking step (so maybe involve, or just make @Martin-Strecker aware of this).

[kharus]

@anka-213 Agree that type definition can be postponed.
I was looking at it yesterday and even haskell LS doesn't implement it properly.