Add .flutter-plugins-dependencies to .gitignore (#146)

Author: Ali Abdelfattah

.gitignore

@@ -103,4 +103,5 @@ lint/tmp/
 !**/ios/**/default.mode2v3
 !**/ios/**/default.pbxuser
 !**/ios/**/default.perspectivev3
-!/packages/flutter_tools/test/data/dart_dependencies_test/**/.packages
+!/packages/flutter_tools/test/data/dart_dependencies_test/**/.packages
+example/.flutter-plugins-dependencies