Add note about (un)shift to (push/pop)first docs

[tckmn]

This would be helpful for new users when searching for these functions via e.g. apropos().

[StefanKarpinski]

Yes, that's a good improvement. Thanks!

[carstenbauer]

Why would one choose unshift as the name for a function that adds an element to the beginning of a collection? Seems super weird to me... Our pushfirst!/popfirst! names are so much better!

On a more general note, since when do we add such references to other programming languages naming conventions to docstrings? Isn't that what the "Noteworthy differences ..." section in the docs is for?

[ararslan]

Isn't that what the "Noteworthy differences ..." section in the docs is for?

I generally assumed that that was for structural/design differences between languages rather than naming/API.

[StefanKarpinski]

That is why we didn't keep those names. Nevertheless that is what these are called in many other languages.