changelog: Document RN v0.68 upgrade

Author: chrisbobbe

docs/changelog.md

@@ -52,6 +52,8 @@ experience.
 
 ### Highlights for developers
 
+* Upgraded to React Native v0.68! (#5610)
+
 * Added a workaround for an iOS build error with "signing requires
   development team". (PR #5576)
 
@@ -64,7 +66,8 @@ experience.
 * We now allow Gradle to use 25% more memory, apparently needed for RN
   v0.68, which we hope to upgrade to soon. (PR #5603)
 
-* Resolved issues: #5592, #5597, #5596, #3469, #5583, #5581, #4386, #5423
+* Resolved issues: #5610, #5592, #5597, #5596, #3469, #5583, #5581, #4386,
+  #5423
 
 
 ## 27.196 (2022-12-01)