Add max and min math functions

[IlanCosman]

It's not super common, but I've found myself wanting these functions to set upper and lower bounds on things.

Obviously this is just a nice tool to have, but as a specific use case, some string commands like pad and repeat will error if you give them negative numbers. Obviously we can't use abs here, so I've been doing test $blah -lt 0 && set $blah 0. This works of course, but it is less elegant and requires setting the value to a variable first.

[ridiculousfish]

Seems reasonable, tinyexpr isn't really set up for functions of arbitrary arity, so it's a bit of a dive, but still a fun isolated change. Start with tinyexpr functions.

[IlanCosman]

This has been implemented. If anyone wants to mark this Fish 3.3, that'd be cool 😄