upgrade demo app

- replaces existing demo app with newly bootstrapped app to avoid painstaking upgrade.
- replaces old UI with simpler more basic UI.
- uses Swift on iOS now
- adds bridging header for obj-c interop

Author: zibs

examples/demo/_bundle/config renamed to examples/demo/.bundle/config

@@ -20,7 +20,7 @@ DerivedData
 *.hmap
 *.ipa
 *.xcuserstate
-ios/.xcode.env.local
+**/.xcode.env.local
 
 # Android/IntelliJ
 #
@@ -33,6 +33,7 @@ local.properties
 .cxx/
 *.keystore
 !debug.keystore
+.kotlin/
 
 # node.js
 #
@@ -56,11 +57,19 @@ yarn-error.log
 *.jsbundle
 
 # Ruby / CocoaPods
-/ios/Pods/
+**/Pods/
 /vendor/bundle/
 
 # Temporary files created by Metro to check the health of the file watcher
 .metro-health-check*
 
 # testing
 /coverage
+
+# Yarn
+.yarn/*
+!.yarn/patches
+!.yarn/plugins
+!.yarn/releases
+!.yarn/sdks
+!.yarn/versions