macOS 12 is officially EOL by Apple and the project only supports
officially supported versions of macOS. Once publicly released, users on
older macOS versions will have to use older released builds.
Add support for configurable fonts for window and tab titles. This is
only implemented for macOS (and could be macOS-only if other platforms
aren't able to support this using their windowing toolkits). It plays
nicely with regular and titlebar tabs.
To do this I forced a toolbar, so that we would have a place to put the
button when no tabs were opened. I also took the opportunity to make the
standard title/tab bar meld better with the terminal's background color,
just as we do with titlebar tabs.
