Update changelog with my recent pushes (#3522)

Author: inlined

CHANGELOG.md

@@ -1,3 +1,6 @@
+- Fix crash when deploying zero functions (#3520)
+- Increase maximum function ID length to 63 (#3521)
+- Delete Container Registry images left after Functions deployment (#3439)
 - Avoid emulator data loss when there an error during export (#3504)
 - Ask before overwriting `storage.rules` during `firebase init` (#1833)
 - Release Cloud Firestore Emulator v1.13.0.