Clean up shim initialization

ext/src/shim/contentBridge.ts

@@ -0,0 +1,15 @@
+"use strict";
+
+import { onMessageResponse, sendMessage } from "./eventMessageChannel";
+
+
+// Message port to background script
+const backgroundPort = browser.runtime.connect({ name: "shim" });
+
+// Forward background messages to shim
+backgroundPort.onMessage.addListener(sendMessage);
+
+// Forward shim messages to background
+onMessageResponse(message => {
+    backgroundPort.postMessage(message);
+});