Revert "Remove custom extension confirmation"

This reverts commit cc670272a2.

No, it's not safe.

src/lib/tw-state-manager-hoc.jsx

@@ -362,7 +362,10 @@ const TWStateManager = function (WrappedComponent) {
             }
 
             for (const extension of urlParams.getAll('extension')) {
-                this.props.vm.extensionManager.loadExtensionURL(extension);
+                // This is temporary until we feel more comfortable about the idea of running remote code in a Worker.
+                if (confirm(`Load extension: ${extension}`)) {
+                    this.props.vm.extensionManager.loadExtensionURL(extension);
+                }
             }
 
             const routerCallbacks = {