Added video demonstration for editing shortcuts

Author: list-jonas

content/docs/user-manual/shortcuts.mdx

@@ -9,7 +9,12 @@ Zen Browser supported lots of keyboard shortcuts to help you do common tasks qui
 
 ### Change or rebind keyboard shortcuts in Zen
 
-{/* TODO: insert video of editing a keyboard shortcuts */}
+<div align="center">
+  <video width="100%" loop autoPlay>
+    <source src="/assets/user-manual/shortcuts/edit-shortcut.mp4" />
+    Your browser does not support the video tag.
+  </video>
+</div>
 
 - In Keyboard Shortcuts setting page, to change or rebind shortcut of a feature, click the text field beside it, press your shortcuts, and press Esc to save your new shortcut.
   - The text field will show a dark green outline quickly when the new shortcut is succesfully assigned and saved.