update .pubignore

.pubignore

-example/
+example/android/gradle/wrapper/gradle-wrapper.jar
+example/build
+
+android/.classpath
+android/.project
+android/.settings/org.eclipse.buildship.core.prefs
+example/android/.project
+example/android/.settings/org.eclipse.buildship.core.prefs
+example/android/app/.classpath
+example/android/app/.project
+example/android/app/.settings/org.eclipse.buildship.core.prefs
+example/ios/.symlinks
+example/Podfile.lock
+.last_build_id
+
+example/build
+example/.dart_tool
+
+example/.flutter-plugins
+example/.flutter-plugins-dependencies
+example/.packages
+example/.pub-cache/
+example/.pub/
+example/build/
+
 .DS_Store
 .dart_tool/