[edition] Add a FreeText editor (#14970)

- add a basic UI to edit some text in a pdf;
- an editor can be moved, suppressed, cut, copied, pasted, selected;
- add an undo/redo manager.

web/app_options.js

@@ -58,6 +58,11 @@ const defaultOptions = {
     value: 2,
     kind: OptionKind.VIEWER + OptionKind.PREFERENCE,
   },
+  annotationEditorEnabled: {
+    /** @type {boolean} */
+    value: typeof PDFJSDev !== "undefined" && PDFJSDev.test("TESTING"),
+    kind: OptionKind.VIEWER + OptionKind.PREFERENCE,
+  },
   cursorToolOnLoad: {
     /** @type {number} */
     value: 0,