2.2.1

Added

• Support for associations.physio and associations.events.sidecar.

• Implement associations.coordsystems to collate multiple coordsystem.json files,
  as required by BEP 042 (EMG).

Changed

• Validation context generation was tweaked to improve concurrency, giving 4x validation
  speedups in some cases.

Pull requests merged

• test: Add opener implementations for tests by @effigies in #283
• feat: Start loading contexts earlier, buffer contexts for better concurrency by @effigies in #282
• BEP020 patches by @effigies in #260
• BEP042 patches by @drammock in #268

Full Changelog: 2.2.0...2.2.1