proto-lens-descriptors-0.2.2.0: Changelog.md

# Changelog for `proto-lens-descriptors`

# Unreleased changes

# v0.2.2.0
- Bump the dependency on `base` to support `ghc-8.2.1`.
- Track latest changes in `proto-lens-protoc`.

## v0.2.1.0 and older
See `Changelog.md` for `proto-lens`.