Update CHANGELOG for 0.25.0
MODIFY
CHANGELOG.md
CHANGELOG.md
Change Log
==========
+## Version 0.25.0
+
+_2020-03-27_
+
+### Kotlin
+
+* Swift-only release. No changes.
+
+### Swift
+
+* Introduce `SignalWorker` to wrap `Signal`s (#1048)
+
## Version 0.24.0
_2020-03-10_

Update CHANGELOG for 0.25.0