Problem: No way to get the arity of a Vim function
(Austin Ziegler)
Solution: Enhance get() Vim script function to return the function
argument info using get(func, "arity") (LemonBoy)
fixes: vim/vim#15097closes: vim/vim#1510948b7d05a4f
Co-authored-by: LemonBoy <thatlemon@gmail.com>