add support for visual selected text

[HandOfGod94]

I wanted the tag search to also work with visually selected text instead of just <cword>.
This is specifically helpful for languages like ruby where method names at times are also represented as symbols.

For .e.g.

def foo
   ....
end 

in DSL libs are often represented as

event :xyz, before: :foo do
 ...
end

This often leads to visually selecting foo and then do a tag search.
This is working for me, and hope will be helpful for others as well.

1 thing to note though, I'm using this snippet to get visually selected text. This modifies a registers. Although it works out for me, I'm not sure if it's ideal for others.

[gnfisher]

👋 Thanks for opening the PR @HandOfGod94. I'm going to try to find some time this weekend.

I'm not sure about using the a register? I'd like to do a little reading before merging and I'll get back to you asap. Thanks for thinking of handling the case and taking the time to contribute the code!