Upgrade TinyMCE to v5.0.12

gui/public/tinymce/skins/ui/oxide-dark/content.mobile.min.css

@@ -0,0 +1,7 @@
+/**
+ * Copyright (c) Tiny Technologies, Inc. All rights reserved.
+ * Licensed under the LGPL or a commercial license.
+ * For LGPL see License.txt in the project root for license information.
+ * For commercial licenses see https://www.tiny.cloud/
+ */
+.tinymce-mobile-unfocused-selections .tinymce-mobile-unfocused-selection{background-color:green;display:inline-block;opacity:.5;position:absolute}body{-webkit-text-size-adjust:none}body img{max-width:96vw}body table img{max-width:95%}body{font-family:sans-serif}table{border-collapse:collapse}