migrate to zat.dev/zat on tangled

README.md

···
 ## install
 
 ```bash
-zig fetch --save https://tangled.sh/zzstoatzz.io/zat/archive/main
+zig fetch --save https://tangled.sh/zat.dev/zat/archive/main
 ```
 
 then in `build.zig`:

site/index.html

···
         <a class="brand" href="./">zat.dev</a>
         <a
           class="header-link"
-          href="https://tangled.org/zzstoatzz.io/zat"
+          href="https://tangled.org/zat.dev/zat"
           target="_blank"
           rel="noopener noreferrer"
         >