Add multibuffer edit video (#14757)

Release Notes:

- N/A

docs/src/multibuffers.md

@@ -4,6 +4,8 @@ One of the superpowers Zed gives you is the ability to edit multiple files simul
 
 ## Editing in a multibuffer
 
+![Editing the results of a search multibuffer.](https://customer-snccc0j9v3kfzkif.cloudflarestream.com/bda0a6584c19f4b39e58a263c0ae4358/downloads/default.mp4)
+
 Editing a multibuffer is the same as editing a normal file. Changes you make will be reflected in the open copies of that file in the rest of the editor, and you can save all files with `editor: Save` (bound to `cmd-s` on macOS, `ctrl-s` on Windows/Linux, or `:w` in Vim mode).
 
 When in a multibuffer, it is often useful to use multiple cursors to edit every file simultaneously. If you want to edit a few instances, you can select them with the mouse (`option-click` on macOS, `alt-click` on Window/Linux) or the keyboard. `cmd-d` on macOS, `ctrl-d` on Windows/Linux, or `gl` in Vim mode will select the next match of the word under the cursor.