Remove `bashly add test` liibrary (`approvals.bash`)

[DannyBen]

The addition of this library was nice at the early days of bashly, but now it is too opinionated, and not necessarly the best practice for testing bash scripts. It should probably be removed. Users should choose their own testing library, without nudging them towards one lib or another.

[meleu]

Indeed, I had this feeling when I came to bashly...

Digressing a bit on this "bash testing" topic: which alternatives do you use?

UPDATE: moved this to a dedicated discussion