Adds `--cache` flag to prettier which significantly speeds up `yarn
format`:
https://prettier.io/docs/en/cli#--cache
One downside is that changing the plugins we use with prettier will not
cause the cache to invalidate. Stills seems worth it though.
> Plugins version and implementation are not used as cache keys. We
recommend that you delete the cache when updating plugins.
### Change Type
- [ ] `patch` — Bug fix
- [ ] `minor` — New feature
- [ ] `major` — Breaking change
- [ ] `dependencies` — Changes to package dependencies[^1]
- [ ] `documentation` — Changes to the documentation only[^2]
- [ ] `tests` — Changes to any test code only[^2]
- [x] `internal` — Any other changes that don't affect the published
package[^2]
- [ ] I don't know
[^1]: publishes a `patch` release, for devDependencies use `internal`
[^2]: will not publish a new version
### Test Plan
1. Run `yarn format`
2. Run `yarn format` again, this time it should be significantly faster.
### Release Notes
- Speed up formatting of files via `yarn format`.
9e7d258b5f