This PR is an internal refactor of the codemods package structure that
will make a few follow-up PRs easier.
Essentially what happens is:
1. Moved `./src/template/` into `src/codemods/template/`
2. Moved `./src/codemods` into `./src/codemods/css` (because the CSS
related codemods already)
3. Moved the migration files for the JS config, PostCSS config and
Prettier config into `./src/codemods/config/`.
4. Made filenames with actual migrations consistent by prefixing them
with `migrate-`.
5. Made sure that all the migration functions also use `migrate…`
When looking at this PR, go commit by commit, it will be easier. In a
lot of cases, it's just moving files around but those commits also come
with changes to the code just to update the imports.
[ci-all]
b94720aef3