More intelligent `:DashWord` using LSP or TreeSitter

[mrjones2014]

Original request from #26

my dream feature would be to use the LSP and/or Treesitter to lookup the docs for the method on the correct object type. In other words, var_that_is_a_tempfile.[o]pen (with the cursor on the o) would open the docs for specifically Tempfile.open.

I'm not sure how we'd implement this but I think it might be possible via LSP info or TreeSitter.