docs: Added warning about Vercel branch deployment (#861)

* docs: Added warning about Vercel branch deployment

Added a note to the Vercel installation section to remind users that they must deploy the 'vercel' branch to avoid 404 errors.

* small adjustment to wording

---------

Co-authored-by: Jonah Lawrence <jonah@freshidea.com>

Author: ArturCharylo

README.md

@@ -176,6 +176,9 @@ Vercel is the recommended option for hosting the files since it is **free** and
 
 #### Option 1: Deploy to Vercel quickly with the Deploy button (recommended)
 
+> [!IMPORTANT]
+> Make sure that you host the **`vercel`** branch as otherwise you'll get a 404 error from Vercel. You can set the `vercel` branch as default after forking the repo.
+
 1. Click the Deploy button below
 
 [![][hspace]](#) [![Deploy with Vercel](https://i.imgur.com/Mb3VLCi.png)][verceldeploy]