add zsdl3 to graphics libraries

Author: felixuxx

README.md

@@ -597,6 +597,7 @@ TOC is generated by [markdown-toc](https://github.com/jonschlinkert/markdown-toc
 - [rockorager/libvaxis](https://github.com/rockorager/libvaxis) - Modern TUI library written in Zig.
 - [zig-plotille](https://github.com/tammoippen/zig-plotille) - Terminal plotting library using Unicode braille characters.
 - [xtxf](https://github.com/charlesrocket/xtxf) - The Matrix screensaver in Zig.
+- [zsdl3](https://github.com/felixuxx/zsdl3) - SDL3 bindings for Zig.
 
 ### GUI