feat: Search functions

[Samigos]

I was thinking of implementing a search for functions to be mentioned on a message, just like the one for searching files on the text editor. I think there would need to be some kind of index of files, so that the search is fast and ready.

My questions are:
Do you think it'll be useful?

If yes:
Should the search panel appear when typing @ and have the results merged with the files results, or have a new tag like #?