Improve font settings for Inter

Not sure what all needs to or can be done, but we're still seeing strange hinting/kerning in places in 6.0 dailies.

Things to try:
- Xsettings hinting (currently `slight`, see dconf `/org/gnome/settings-daemon/plugins/xsettings/hinting`)
- antialiasing (currently `rgba`, probably should change to `grayscale`)
- Default font size (currently 9, would need to be tweaked in the stylesheet `rem()` function, too)
- Trying Ubuntu package vs. latest Windows hinted version vs. latest Desktop version
- Freetype settings
- see: https://bugs.launchpad.net/ubuntu/+source/freetype/+bug/1722508
- https://www.freetype.org/freetype2/docs/reference/ft2-lcd_rendering.html
- https://www.freetype.org/freetype2/docs/subpixel-hinting.html

I'm unsure what else could be investigated. I'm aware this is a sort of catch-all issue, but I figured having a public place to investigate and share findings was a better start than opening a whole bunch of issues before we know what we actually need to do.