Pin Prettier versions for consistent formatting

[AndrewSazonov]

• Pin Prettier and the TOML plugin to prevent local/CI version drift.
• Enable aligned trailing TOML comments.
• Document refreshing development tools after Copier updates.

Fixes #57

[seventil]

Pinning the version would solve the local/ci version drift, but we'll have to remember to update the version manually then.
If we don't pin, the local/ci version drift might lead up to CI failure and that would indicate to upgrade the version.

Seems that neither choice is a better one, just a preference, I'm ok with pinning.