Publish flutter v0.13.0

Diffs=
ef100e0d9 Publish flutter v0.13.0 (#6808)

Co-authored-by: Philip Chung <philterdesign@gmail.com>

.rive_head

@@ -1 +1 @@
-99a2215daeffdfe537e2a900113a9d59ee7b9d3f
+ef100e0d9462f9f71b0be53a0abdc2f438afeb92

CHANGELOG.md

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-## Upcoming
+## 0.13.0
 
+- Adds support for Audio.
+- Object Generator adds the ability to override built-in objects with custom objects.
 - Fix [[355](https://github.com/rive-app/rive-flutter/issues/355)] to ensure the Rive render object is attached before handling pointer events.
 
 ## 0.12.4

pubspec.yaml

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 name: rive
-version: 0.12.4
+version: 0.13.0
 homepage: https://rive.app
 description: Rive 2 Flutter Runtime. This package provides runtime functionality for playing back and interacting with animations built with the Rive editor available at https://rive.app.
 repository: https://github.com/rive-app/rive-flutter