Truncate border titles

[Conni2461]

@delphinus i wrote you in gitter private but you haven't answered so i might try this way.

I wanna move your truncate code from telescope into plenary so we can use it to truncate border titles. See nvim-telescope/telescope.nvim#528 (comment)
I just wanted to ask if you want to do it because you wrote most of that amazing code. :)

I would remove the code in telescope afterwards, in the #528 PR

[delphinus]

Oh, sorry for it in gitter. OK I'll transfer the code into here. Wait a minute.

[delphinus]

I created #96 and ported funcs that is ported from VimL ones.

• strdisplaywidth()
• strcharpart()
• entry_display.truncate()

And I'll put PR to use these funcs from telescope.nvim itself.

[delphinus]

And I added another one.

• align_str()

[Conni2461]

This was implemented