Implement Fish shell features

[hydralisk98]

Simply curious if it would be good to implement shell features from the more recent Fish one instead on relying mostly onto POSIX-compliance. Thank you for hosting the project and here is the reference I am referring back to just in case: https://fishshell.com/

Might also consider a few more system "shells" such as HundredRabbits' Paradise/Parade, but that might be left to another issue really.

I am likely to implement most if not all of such myself in due time so no worries.