v0.21.0

Breaking change

• The API for the chainsync protocol has changed. There is now a single entry point, and you only need to provide handler functions for roll forward/backward

What's Changed

• feat: make the chainsync interface friendlier by @agaffney in #132
• feat: finish implementing local-state-query by @agaffney in #133
• feat: flesh out query result types by @agaffney in #135

Full Changelog: v0.20.0...v0.21.0