open-witness-0.7: changelog.md

## [0.7] - 2024-12-15
- update for witness-0.7
- fix for GHC 9.8, 9.10

## [0.6] - 2022-05-10
- update for witness-0.6
- move module hierarchy
- Witnessed now synonym for PairType IOWitness

## [0.5] - 2020-09-22