HexEditor: Add comments to annotations

The comment appears as a tooltip when hovering over the annotation.

A couple of properties of the TextEditor would ideally be set in GML,
but either don't have a setter exposed, or the GML compiler doesn't
recognise the enum. I'll fix those up after the current big GML
compiler PR gets merged.

Userland/Applications/HexEditor/EditAnnotationWidget.gml

@@ -54,6 +54,22 @@
         }
     }
 
+    @GUI::Widget {
+        layout: @GUI::VerticalBoxLayout {
+            margins: [4]
+        }
+        preferred_height: "fit"
+
+        @GUI::Label {
+            text: "Comments:"
+            text_alignment: "CenterLeft"
+        }
+
+        @GUI::TextEditor {
+            name: "comments"
+        }
+    }
+
     @GUI::Widget {
         layout: @GUI::HorizontalBoxLayout {
             margins: [4]