chore: prepare for release 3.10.0 (#458)

## Summary
- prepare for release 3.10.0

CHANGELOG.md

@@ -1,5 +1,17 @@
 # Optimizely Java X SDK Changelog
 
+## 3.10.0
+January 10th, 2022
+
+### New Features
+* Add a set of new APIs for overriding and managing user-level flag, experiment and delivery rule decisions. These methods can be used for QA and automated testing purposes. They are an extension of the OptimizelyUserContext interface ([#451](https://github.com/optimizely/java-sdk/pull/451), [#454](https://github.com/optimizely/java-sdk/pull/454), [#455](https://github.com/optimizely/java-sdk/pull/455), [#457](https://github.com/optimizely/java-sdk/pull/457))
+  - setForcedDecision
+  - getForcedDecision
+  - removeForcedDecision
+  - removeAllForcedDecisions
+
+- For details, refer to our documentation pages: [OptimizelyUserContext](https://docs.developers.optimizely.com/full-stack/v4.0/docs/optimizelyusercontext-java) and [Forced Decision methods](https://docs.developers.optimizely.com/full-stack/v4.0/docs/forced-decision-methods-java).
+
 ## [3.9.0]
 September 16th, 2021