Add ~ to completion items when insert-text

[ericdallo]

This is a simple modification to enhance completion doing the same neovim does, showing a ~ on the end of the completion item if it will insert some kind of text rather than just the label, this is useful to user know that this completion item will do something other than just complete with the label.

Note: We can't rely only on snippet kind since it's possible and IMO makes sense for example to return a completion item saying that an item is of type function but will insert some other kind of text like clojure and rust, example:

lsp-mode

neovim

c/c @kiennq @yyoncho

For curiosity, I realized that on this issue

[yyoncho]

Can you have this behind a flag and turned off by default? I haven't seen anything like that in other ides and I don't think that neovim can be our UE guideline. We tend to follow the VSCode.

[kiennq]

Can we use company-mode annotation for this instead?
That would also had better performance since we only adding the annotations for visible candidates instead of the whole list

[ericdallo]

I didn't know about annotation, sounds good, I'll change it

[kiennq]

Also, if we're using :annotation-function then we can do more accurate comparisons there, i.e,: compare the label to insert-text to make sure the display and the inserted is not the same, compare the edit-text as well if possible.

[diaevd]

I didn't know about annotation, sounds good, I'll change itI

I'm make similar changes with the company-transform function. Why change something at the lsp-completion level? For me this change will be breaking change