automate update of CHANGELOG when bumping version

[Remi-Gau]

see here for some starters: https://github.com/bids-standard/bids-specification/blob/c27f613c779ba75e35397576998ccf388cfb8943/.circleci/config.yml#L65

[Remi-Gau]

closing this for now as the github tools to do this manually are more than decent

we can still reopen if we need more automation