v0.7.1

A small release: a Rust sync recipe, YAML formatting, and clearer docs. Nothing breaks.

What changes in your project

• just rs-sync downloads Rust dependencies and writes Cargo.lock, like
  just py-sync, just ts-sync and just go-sync do for their stacks.
• A yamlfmt hook formats YAML files. yamllint now checks yamlfmt's output, and
  flow mappings are written {key: value}.
• Hook revs are commit SHAs, with a # frozen: comment naming the tag, because
  tags can move. Dependabot updates both together.
• Comments and docstrings in generated files are shorter and plainer.

Upgrading from v0.7.0

1. Run copier update.
2. Run prek run -a once, so yamlfmt formats your existing YAML files.

The full list is in
CHANGELOG.md.