Explore variable-width font feature added in PICO8 0.2.5 release

[icegoat9]

Since I'm already moving to PICO8 custom fonts for icons for a v1.1 under-the-hood revision of PICOhaven, I could also use a variable-width custom font to handle the width adjustments (for " ", ":", etc) I make to a few characters.

But this likely adds more tokens vs. the current "rewrite strings with -f before printing" approach, so not going to do it for now, unless I find another reason to use variable-width fonts such as a broader custom font.