chore: add flutter quickstart example, assets and update README

examples/flutter/quickstart/pubspec.yaml

@@ -0,0 +1,40 @@
+name: quickstart
+description: "A new Flutter project."
+publish_to: 'none' # Remove this line if you wish to publish to pub.dev
+
+version: 1.0.0+1
+
+environment:
+  sdk: '>=3.3.0 <4.0.0'
+
+dependencies:
+  flutter:
+    sdk: flutter
+  cupertino_icons: ^1.0.8
+  vector_math: ^2.1.4
+
+  win32: 5.5.1
+  web: 1.0.0
+  thermion_flutter: ^0.2.1-dev.7
+
+dev_dependencies:
+  flutter_test:
+    sdk: flutter
+  flutter_lints: ^4.0.0
+
+dependency_overrides:
+  thermion_dart:
+    path: /Users/nickfisher/Documents/polyvox/apps/packages/thermion/thermion_dart
+  thermion_flutter_web:
+    path: /Users/nickfisher/Documents/polyvox/apps/packages/thermion/thermion_flutter/thermion_flutter_web
+  thermion_flutter:
+    path: /Users/nickfisher/Documents/polyvox/apps/packages/thermion/thermion_flutter/thermion_flutter
+  thermion_flutter_platform_interface:
+    path: /Users/nickfisher/Documents/polyvox/apps/packages/thermion/thermion_flutter/thermion_flutter_platform_interface
+  thermion_flutter_ffi:
+    path: /Users/nickfisher/Documents/polyvox/apps/packages/thermion/thermion_flutter/thermion_flutter_ffi
+
+flutter:
+  uses-material-design: true
+  assets:
+    - assets/