ROI / Scholia, v2

[jacobwegner]

Follows Add regions of interest highlighting #75.

Will circle back on the FIXMEs and TODOs via https://github.com/scaife-viewer/beyond-translation-site/issues/177

Features

• See ROI annotations when viewing in "image-only" mode
• Highlight scholia without lemma values
• Tweak OpenSeaDragon to improve maximum zoom in / out settings
• Mimic border / background colors from HMT
• Add color legend to widget-scholia

Fixes

• Ensures consistent viewport height

Other Improvements

• Migrate to Yarn v2

[jacobwegner]

Upgrading to Yarn "Berry" has broken our CI; I'm going to merge this for now and circle back to fix the CI in another PR.