Uds 1442- Add changelog and license to packages

[davidornelas11]

Description

All packages need to contain License and changelog files. unity-bootstrap-theme contains upgrade.md

Create prepublish script to copy root license to all packages during build and publish. This makes it easier to keep a single source of truth for the license and it only needs to be edited in one place for all files to be updated. Added CHANGELOG to all packages as well

Links

• JIRA ticket

Checklist

• [x] Unity project successfully builds from root yarn install & yarn build
• [ ] Commits do not contain multiple scopes
• [x] Add/updated examples
• [x] Add/updated READMEs/docs
• [x] No new console errors
• [x] Accessibility checks