Extend the functionality of hover in rbs files.

[Yuuki77]

add hover supports for RBS::Types::ClassInstance, RBS::Types::ClassSingleton and RBS::Types::Interface.

When these are hovered, the information and comments will now be displayed!

How to test

crate a rbs file with this content and you can confirm that you can see the information when you hover them

# my comment
class Foo [T] < Parent[T]
end

class Parent [in T]
end

module Hoge
end

class Qux
  @foo: Foo[Hoge]
end

interface _Fooable
  def foo: () -> nil
end

class C
  def foo: (_Fooable) -> singleton(String)
end

[soutaro]

The rest of the code looks good.

[soutaro]

Use location[:name] here to highlight only name of the interface.

[Yuuki77]

@soutaro Thank you for the reviews!
I have updated it 1545d6b

[soutaro]

💪