Add Prettier to the repo, and format all the files! (#428)

This adds prettier to the repo, and sets up the pre-commit hook to
auto-format as well as lint.
Also updates ignores files to exclude crawls, test-crawls, scratch, dist as needed.

.husky/pre-commit

@@ -1,4 +1,4 @@
 #!/usr/bin/env sh
 . "$(dirname -- "$0")/_/husky.sh"
 
-yarn lint
+yarn lint:fix