Update changelog for v0.3.0 (#2421)

## Description

Updating CHANGELOG file prepping for new release.

## Does this PR need a docs update or release note?

- [ ] ✅ Yes, it's included
- [ ] 🕐 Yes, but in a later PR
- [x] ⛔ No 

## Type of change

<!--- Please check the type of change your PR introduces: --->
- [ ] 🌻 Feature
- [ ] 🐛 Bugfix
- [x] 🗺️ Documentation
- [ ] 🤖 Test
- [ ] 💻 CI/Deployment
- [ ] 🧹 Tech Debt/Cleanup

## Issue(s)

<!-- Can reference multiple issues. Use one of the following "magic words" - "closes, fixes" to auto-close the Github issue. -->
* #<issue>

## Test Plan

<!-- How will this be tested prior to merging.-->
- [ ] 💪 Manual
- [ ] ⚡ Unit test
- [ ] 💚 E2E

CHANGELOG.md

@@ -7,6 +7,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased] (alpha)
 
+## [v0.3.0] (alpha) - 2023-2-07
+
 ### Added
 
 - Document Corso's fault-tolerance and restartability features
@@ -156,7 +158,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Miscellaneous
   - Optional usage statistics reporting ([RM-35](https://github.com/alcionai/corso-roadmap/issues/35))
 
-[Unreleased]: https://github.com/alcionai/corso/compare/v0.2.0...HEAD
+[Unreleased]: https://github.com/alcionai/corso/compare/v0.3.0...HEAD
+[v0.3.0]: https://github.com/alcionai/corso/compare/v0.2.0...v0.3.0
 [v0.2.0]: https://github.com/alcionai/corso/compare/v0.1.0...v0.2.0
 [v0.1.0]: https://github.com/alcionai/corso/compare/v0.0.4...v0.1.0
 [v0.0.4]: https://github.com/alcionai/corso/compare/v0.0.3...v0.0.4