added "edit" button into ribbon button container

src/public/app/widgets/buttons/edit_button.js

@@ -0,0 +1,31 @@
+import ButtonWidget from "./button_widget.js";
+
+export default class EditButton extends ButtonWidget {
+    isEnabled() {
+        return super.isEnabled() && this.noteContext;
+    }
+
+    constructor() {
+        super();
+
+        this.icon("bx-edit-alt")
+            .title("Edit this note")
+            .titlePlacement("bottom")
+            .onClick(widget => {
+                this.noteContext.readOnlyTemporarilyDisabled = true;
+
+                this.triggerEvent('readOnlyTemporarilyDisabled', {noteContext: this.noteContext});
+
+                this.refresh();
+            });
+    }
+
+    async refreshWithNote(note) {
+        // can't do this in isEnabled() since isReadOnly is async
+        this.toggleInt(await this.noteContext.isReadOnly());
+
+        console.log("await this.noteContext.isReadOnly()", await this.noteContext.isReadOnly());
+
+        await super.refreshWithNote(note);
+    }
+}