Add syncthing ignore files

ios/.stignore

@@ -0,0 +1,33 @@
+/**/dgph
+/*.mode1v3
+/*.mode2v3
+/*.moved-aside
+/*.pbxuser
+/*.perspectivev3
+/**/*sync/
+/.sconsign.dblite
+/.tags*
+/**/.vagrant/
+/**/DerivedData/
+/Icon?
+/**/Pods/
+/**/.symlinks/
+/profile
+/xcuserdata
+/**/.generated/
+/Flutter/App.framework
+/Flutter/Flutter.framework
+/Flutter/Flutter.podspec
+/Flutter/Generated.xcconfig
+/Flutter/ephemeral/
+/Flutter/app.flx
+/Flutter/app.zip
+/Flutter/flutter_assets/
+/Flutter/flutter_export_environment.sh
+/ServiceDefinitions.json
+/Runner/GeneratedPluginRegistrant.*
+
+!default.mode1v3
+!default.mode2v3
+!default.pbxuser
+!default.perspectivev3