Portable way to force use of monospaced font in TADS3/adv3?

[ArdiMaster (Adrian)]

@inventor200

I keep hearing from the Parchment/Gargoyle team(s) that support for more TADS markup (beyond just bold and italics) is still on the way.

I’ve finally gotten around to opening a pull request that should enable proper handling of <tt> (and also <pre>) for Glk-based interpreters.