docs(readme): embed ship-demo.gif showing nextdeploy ship end-to-end

Real screencast of editing a Next.js component, running `nextdeploy ship`,
and landing live on Cloudflare. Centered between the install one-liner and
Quick start so the README leads with proof of the deploy flow.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: aynaash

README.md

@@ -9,6 +9,10 @@ curl -fsSL https://nextdeploy.org/install.sh | bash
 
 Windows: download `install.bat` from <https://nextdeploy.org/install.bat>.
 
+<p align="center">
+  <img src="./assets/ship-demo.gif" alt="nextdeploy ship — edit a Next.js component and deploy to Cloudflare in seconds (2× speed, no edits)" width="820" />
+</p>
+
 ## Quick start
 
 ```bash