update image size

README.md

@@ -6,7 +6,7 @@
 
 vger is a vector graphics renderer which renders a limited set of primitives, but does so almost entirely on the GPU. Works on iOS and macOS. API is plain C. Rust port is [here](https://github.com/audulus/vger-rs).
 
-<img src="demo.png" alt="demo" width="256" height="256">
+<img src="demo.png" alt="demo" width="300" height="450">
 
 Each primitive can be filled with a solid color, gradient, or texture. vger renders primitives as instanced quads, with most of the calculations done in the fragment shader.