Adding shrine. (#3)

Adds a new version of Shrine from the MDC codelabs.

shrine/ios/.gitignore

@@ -0,0 +1,45 @@
+.idea/
+.vagrant/
+.sconsign.dblite
+.svn/
+
+.DS_Store
+*.swp
+profile
+
+DerivedData/
+build/
+GeneratedPluginRegistrant.h
+GeneratedPluginRegistrant.m
+
+.generated/
+
+*.pbxuser
+*.mode1v3
+*.mode2v3
+*.perspectivev3
+
+!default.pbxuser
+!default.mode1v3
+!default.mode2v3
+!default.perspectivev3
+
+xcuserdata
+
+*.moved-aside
+
+*.pyc
+*sync/
+Icon?
+.tags*
+
+/Flutter/app.flx
+/Flutter/app.zip
+/Flutter/flutter_assets/
+/Flutter/App.framework
+/Flutter/Flutter.framework
+/Flutter/Generated.xcconfig
+/ServiceDefinitions.json
+
+Pods/
+.symlinks/