update readme to recommend Zig 0.15.2 and -Drelease

Author: Techatrix

README.md

@@ -9,10 +9,10 @@ You can either:
 - Use it online: https://playground.zigtools.org/
 - Run it locally:
 
-Requires Zig `0.15.1`. Will automatically fetch Zig along with ZLS, compiling both for webassembly.
+Requires Zig `0.15.2`. Will automatically fetch Zig along with ZLS, compiling both for webassembly.
 
 ```bash
-zig build
+zig build -Drelease
 npm install
 npm run dev
 ```