JS -- Implement app object

* https://www.adobe.com/content/dam/acom/en/devnet/acrobat/pdfs/AcrobatDC_js_api_reference.pdf
 * Add color, fullscreen objects + few constants.

src/display/annotation_layer.js

@@ -15,6 +15,7 @@
 
 import {
   addLinkAttributes,
+  ColorConverters,
   DOMSVGFactory,
   getFilenameFromUrl,
   LinkTarget,
@@ -567,6 +568,12 @@ class TextWidgetAnnotationElement extends WidgetAnnotationElement {
                   event.target.setSelectionRange(selStart, selEnd);
                 }
               },
+              strokeColor() {
+                const color = detail.strokeColor;
+                event.target.style.color = ColorConverters[`${color[0]}_HTML`](
+                  color.slice(1)
+                );
+              },
             };
             for (const name of Object.keys(detail)) {
               if (name in actions) {