Add test that asserts JavaScript goody and TypeScript goody code is prettified

After #149, we won't be running Prettier on the resulting code in the browser. This should save some extra work but it means there's no guarantee that the code is optimally pretty. As part of the snapshot tests that try to render or equip individual goodies, let's additionally assert that the JS or TS code would be unchanged if run through Prettier!

Locate the snapshot tests that render or equip individual goodies, then inspect how JavaScript and TypeScript outputs are produced after #149. Run the existing snapshot test suite first. Done means the tests assert that each JS or TS result is unchanged when formatted with Prettier.

Written by the indexing model from the issue text.