Integration for blink.cmp

Hello, here's the integration with blink.cmp as I mentioned on #34. I took the implementation of `nvim-cmp` as a base and made a little adjustment to compensate for the "lack" of an offset provided by the context of `blink.cmp`, it works but there may be some room for improvements. @RicardoRamirezR At first I thought about implementing it so it would integrate seamlessly as `nvim-cmp` or `coq`, but I think it's better if the configuration for `blink.cmp` varies a little to follow their documentation. Minor changes: - Moved the function `extract_inner_function` from `cmp.lua` to `utils.lua`, so it can be used by the two integrations. - Also I added the tags for the *vim documentation file.