Rather than scanning directories and reading in ~230 files on startup,
do the scan at build time so that we're parsing from memory rather
than local storage.
This should shave a bit of time off the startup, although I
haven't measured this, and I've only run this on a remote
linux system thus far.
refs: https://github.com/wez/wezterm/issues/264
This is untested beyond eyeballing the locally generated file.
Will need to make a couple of tags to test this for sure.
refs: https://github.com/wez/wezterm/issues/209
