Hide button that enables the TweetDeck Preview

Closes #356

resources/Content/.all.js

@@ -67,6 +67,7 @@ import setup_tweet_context_menu from "./tweetdeck/setup_tweet_context_menu.js";
 import setup_tweetduck_account_bamboozle from "./tweetdeck/setup_tweetduck_account_bamboozle.js";
 import setup_video_player from "./tweetdeck/setup_video_player.js";
 import skip_pre_login_page from "./tweetdeck/skip_pre_login_page.js";
+import tweetdeck_preview_warning from "./tweetdeck/tweetdeck_preview_warning.js";
 import update from "./update/update.js";
 
 const globalFunctions = [

resources/Content/tweetdeck/tweetdeck.css

@@ -133,6 +133,14 @@ button {
   bottom: 192px !important;
 }
 
+/***********************/
+/* Hide Preview button */
+/***********************/
+
+.js-gryphon-beta-btn {
+  display: none !important;
+}
+
 /*************************************/
 /* Tweak collapsed left panel layout */
 /*************************************/

resources/Content/tweetdeck/tweetdeck_preview_warning.js

@@ -0,0 +1,7 @@
+import { $TD } from "../api/bridge.js";
+
+export default function() {
+	if (!("TD" in window)) {
+		$TD.alert("warning", "Some TweetDuck features failed to load. This might happen if your Twitter account is enrolled into the TweetDeck Preview, which TweetDuck does not support. Try opting out of the TweetDeck Preview to restore TweetDuck's functionality.");
+	}
+}