feat(lsp): goto type reference

[kobyhallx]

Consider snippet

struct Foo {
    x: Field
}

fn foo_func() -> Foo {
    Foo { x: 3 }
}

fn main(x: Field) {
    let foo: Foo = foo_func();

    assert(foo.x != x);
}

User should be able to navigate to definition of struct Foo from a symbol Foo in line fn foo_func() -> Foo { and be taken to struct Foo { line.