Adding dynamic_theme and gemini_tasks (#2287)

Adds two new samples that use the Google Generative AI SDK for Dart.
Both were created by @rodydavis. I'm merely the uploader so to speak.

## Pre-launch Checklist

- [X] I read the [Flutter Style Guide] _recently_, and have followed its
advice.
- [X] I signed the [CLA].
- [X] I read the [Contributors Guide].
- [X] I updated/added relevant documentation (doc comments with `///`).
- [X] All existing and new tests are passing.

dynamic_theme/pubspec.yaml

@@ -0,0 +1,22 @@
+name: dynamic_theme
+description: "Sample app for the google_generative_ai package"
+publish_to: 'none'
+version: 1.0.0+1
+environment:
+  sdk: '>=3.3.0 <4.0.0'
+
+dependencies:
+  flutter:
+    sdk: flutter
+  flutter_markdown: ^0.7.1
+  google_generative_ai: ^0.3.3
+  url_launcher: ^6.2.6
+
+dev_dependencies:
+  flutter_test:
+    sdk: flutter
+  flutter_lints: ^3.0.0
+
+flutter:
+  uses-material-design: true
+