Add a prompt to launch Element X on mobile

This shows a bottom sheet on mobile asking the user whether they want to open the call in Element X, as soon as the page is loaded.

public/locales/en-GB/app.json

@@ -27,6 +27,7 @@
   "Close": "Close",
   "Confirm password": "Confirm password",
   "Connectivity to the server has been lost.": "Connectivity to the server has been lost.",
+  "Continue in browser": "Continue in browser",
   "Copied!": "Copied!",
   "Copy": "Copy",
   "Copy and share this call link": "Copy and share this call link",
@@ -70,9 +71,11 @@
   "Not encrypted": "Not encrypted",
   "Not now, return to home screen": "Not now, return to home screen",
   "Not registered yet? <2>Create an account</2>": "Not registered yet? <2>Create an account</2>",
+  "Open in the app": "Open in the app",
   "Password": "Password",
   "Passwords must match": "Passwords must match",
   "Profile": "Profile",
+  "Ready to join?": "Ready to join?",
   "Recaptcha dismissed": "Recaptcha dismissed",
   "Recaptcha not loaded": "Recaptcha not loaded",
   "Reconnect": "Reconnect",
@@ -82,6 +85,7 @@
   "Retry sending logs": "Retry sending logs",
   "Return to home screen": "Return to home screen",
   "Select an option": "Select an option",
+  "Select app": "Select app",
   "Send debug logs": "Send debug logs",
   "Sending debug logs…": "Sending debug logs…",
   "Sending…": "Sending…",