chore: cache Prettier runs

[HonkingGoose]

Changes:

• Cache the result from earlier Prettier runs, to speed up running Prettier at a later time

Context:

You can cache the result of Prettier runs locally. That way:

• The first run is a bit slower (due to needing to write a cache file)
• But later Prettier runs will only check files that change, so it's really fast

Docs

Read the Prettier docs for the CLI, --cache config option to learn the full details.