feat(flame_3d): Fix minor nits on flame_3d

packages/flame_3d/README.md

@@ -74,7 +74,7 @@ checkout a specific Flutter build. Thankfully we were able to simplify that proc
 one-liner:
 
 ```sh
-cd $(dirname $(which flutter)) && && git fetch && git checkout bcdd1b2c481bca0647beff690238efaae68ca5ac -q && echo "Engine commit: $(cat internal/engine.version)" && cd - >/dev/null
+cd $(dirname $(which flutter)) && git fetch && git checkout bcdd1b2c481bca0647beff690238efaae68ca5ac -q && echo "Engine commit: $(cat internal/engine.version)" && cd - >/dev/null
 ```
 
 This will check out the GIT repo of your Flutter installation to the specific commit that we require

packages/flame_3d/example/.gitignore

@@ -0,0 +1,43 @@
+# Miscellaneous
+*.class
+*.log
+*.pyc
+*.swp
+.DS_Store
+.atom/
+.buildlog/
+.history
+.svn/
+migrate_working_dir/
+
+# IntelliJ related
+*.iml
+*.ipr
+*.iws
+.idea/
+
+# The .vscode folder contains launch configuration and tasks you configure in
+# VS Code which you may wish to be included in version control, so this line
+# is commented out by default.
+#.vscode/
+
+# Flutter/Dart/Pub related
+**/doc/api/
+**/ios/Flutter/.last_build_id
+.dart_tool/
+.flutter-plugins
+.flutter-plugins-dependencies
+.pub-cache/
+.pub/
+/build/
+
+# Symbolication related
+app.*.symbols
+
+# Obfuscation related
+app.*.map.json
+
+# Android Studio will place build artifacts here
+/android/app/debug
+/android/app/profile
+/android/app/release