Preserve inline comments inside sig blocks during RBS translation

[KaanOzkan]

Comments inside sig do params(...) end blocks were silently dropped because the entire sig node byte range was replaced with the RBS string. Collect any comments within the sig node's range and prepend them to the output before the #: annotation.

Resolves #900

[Morriar]

I think we should force multi line rendering when we find comments.

Consider this:

params(
  # Some documentation
  a: Integer
).void
def foo(a); end

when translated we get this:

# Some documentation
#: (a) -> void
def foo(a); end

it will look as if the documentation is about foo and not a.

[KaanOzkan]

Hmm yeah this makes sense. I think we can either:

1. Associate comments with parameters in RBI and teach RBSPrinter about outputting it
2. Keep doing the string post-processing in Spoom, similar to the new add_inline_sig_comments. We could figure out the multiline aspect by looking at the indentation and insert the comment to the relevant line. We'd also need to add a new flag or set max_line_length to 0 for the RBSPrinter to print multiline comment.

I'm leaning towards 1 since we're getting too much into the printing territory. Wdyt?

[Morriar]

Yes, 1. 👍