Editors: Added lexical editor for testing

Started basic playground for testing lexical as a new WYSIWYG editor.
Moved out tinymce to be under wysiwyg-tinymce instead so lexical is the
default, but TinyMce code remains.

resources/js/wysiwyg-tinymce/scrolling.js

@@ -0,0 +1,29 @@
+/**
+ * @param {Editor} editor
+ * @param {String} scrollId
+ */
+function scrollToText(editor, scrollId) {
+    const element = editor.dom.get(encodeURIComponent(scrollId).replace(/!/g, '%21'));
+    if (!element) {
+        return;
+    }
+
+    // scroll the element into the view and put the cursor at the end.
+    element.scrollIntoView();
+    editor.selection.select(element, true);
+    editor.selection.collapse(false);
+    editor.focus();
+}
+
+/**
+ * Scroll to a section dictated by the current URL query string, if present.
+ * Used when directly editing a specific section of the page.
+ * @param {Editor} editor
+ */
+export function scrollToQueryString(editor) {
+    const queryParams = (new URL(window.location)).searchParams;
+    const scrollId = queryParams.get('content-id');
+    if (scrollId) {
+        scrollToText(editor, scrollId);
+    }
+}