🀜πŸ’₯πŸ•·πŸ’₯πŸ€› Fixed bug where you can't @mention in the middle of a sentence

(Video shows the bug.)

Had to dump regex yet again, because it's shown to be too hard to fix for edge UI cases like this (where you have to insert the username in between words). Or I simply am too tired to try...

.replace(/@(\w+)$|@$/)

In the end, used another part of the awesome code from the [textarea-caret-position](https://github.com/component/textarea-caret-position) repo. It used a combo of all Javascript methods - slice, split, endsWith, substr, setSelectionRange. More convoluted, not as elegant and simple as regex, but it gets the job done.

The above was for selection on keydown of enter key. Also removed regex from mouse click selection too.