Implement the hardware keyboard interface (#297)

Author: swift-kim

shell/platform/tizen/BUILD.gn

@@ -112,6 +112,7 @@ template("embedder") {
       "channels/app_control_channel.cc",
       "channels/feedback_manager.cc",
       "channels/key_event_channel.cc",
+      "channels/key_mapping.cc",
       "channels/lifecycle_channel.cc",
       "channels/navigation_channel.cc",
       "channels/platform_channel.cc",