Add async and async_wrap from telescope pr

[oberblastmeister]

from pr

[kkharji]

😍 a place where we can have useful abstraction over loop. NICE!!

[kkharji]

simple @Usage examples will be appreciate it as well as tests look at /tests/auto/curl_spec.lua for inspiration

[tjdevries]

I need to read up a bit more on the actual implementation of this and how Neovim is embedding libuv again before I can merge (since we may want to do some other things here).

We should also add safe_async to check the type of the arugments passes so that we cannot crash the editor :) the other can be use at your own risk.