chore: Add changelog items.

Author: fuzzybinary

src/dart/godot_dart/CHANGELOG.md

@@ -1,3 +1,9 @@
+## 0.5.0
+
+- Variant can now be constructed from an Object without using `fromObject`
+- Variants that had `.fromGDString` now also have `.fromString` constructors
+- Added `CallbackAwaiter` which allows you to await a Callable being called.
+
 ## 0.4.0
 
 - Improve Global Class hot reload by having the generator create a list of available global classes.