Changelog updates

[kathryn-ods]

Overview

• What does this pull request do? updates the changelog
• How can a reviewer test or examine your changes?
• Who is best placed to review it?

Closes #555

Translations

• [ ] New or edited strings appearing as a result of this PR will be picked up for translation
• [ ] I've notified the translation coordinator of any new strings that will need translating. See: https://openownership.github.io/bods-dev-handbook/translations.html

Documentation & Release

• [ ] I've checked that the documentation builds without failing. See: https://github.com/openownership/data-standard#building-the-documentation-locally
• [ ] I've thought about how and when this needs to be released. See: https://openownership.github.io/bods-dev-handbook/standard_releases.html
• [ ] I've updated the changelog, if necessary.
• [ ] I've updated reference.rst to reflect any changes to schema structure or naming.
• [ ] I've added or edited any other related documentation. See: https://github.com/openownership/bods-dev-handbook/blob/master/style_guide.md

[kd-ods]

@kathryn-ods - I just cast my eye over this. Would it be OK if we made this a draft PR for the moment, and then I take a run at editing the changelog on this branch in line with https://keepachangelog.com/en/0.3.0/ tomorrow?

[kathryn-ods]

@kd-ods that sounds good! I haven't come across those guidelines before - will have a read :)