Built using:
```
./FontForge-2020-11-07-21ad4a1-x86_64.AppImage --script $PWD/font-patcher "$PWD/src/unpatched-fonts/NerdFontsSymbolsOnly/NerdFontsSymbolsOnly Template 1000 em.ttf" --powerline --use-single-width-glyphs -out /tmp/nerd-fonts-out --fontawesome --fontawesomeextension --fontlinux --octicons --codicons --powersymbols --powerline --powerlineextra --mdi --weathericons
```
which is everything *except* Pomicons at the time of writing, pending
clarifications of its distribution license
(https://github.com/ryanoasis/nerd-fonts/issues/266)
refs: https://github.com/wez/wezterm/issues/1521
The default we use on macOS looks decent. Roboto is a similar
looking font that we can use for the other platforms.
I may make it the same on all three once I've had a chance
to compare it on a mac.
These serve two purposes:
* Provide a consistent default font for new installations,
that happens to show off ligature and color emoji support
out of the box.
* Provide a reasonable fallback in case the configuration is broken
Both fonts are distributed under the terms of the OFL 1.1.
refs: https://github.com/wez/wezterm/issues/263
