Lexical: Added tracked container, added fullscreen action

Changed how the editor is loaded in, so it now creates its own DOM, and
content is passed via creation function, to be better self-contained.

resources/sass/_editor.scss

@@ -4,11 +4,25 @@
 }
 
 // Main UI elements
+.editor-container {
+  background-color: #FFF;
+  position: relative;
+  &.fullscreen {
+    z-index: 500;
+  }
+}
 .editor-toolbar-main {
   display: flex;
   flex-wrap: wrap;
 }
 
+body.editor-is-fullscreen {
+  overflow: hidden;
+  .edit-area {
+    z-index: 20;
+  }
+}
+
 // Buttons
 .editor-button {
   border: 1px solid #DDD;