change max anisotropy to 16

src/main.cpp

@@ -1148,7 +1148,7 @@ int main(int argc, char **argv) {
         .address_mode_v = SDL_GPU_SAMPLERADDRESSMODE_CLAMP_TO_EDGE,
         .address_mode_w = SDL_GPU_SAMPLERADDRESSMODE_CLAMP_TO_EDGE,
 
-        .max_anisotropy    = 4.0f,
+        .max_anisotropy    = 16.0f,
         .enable_anisotropy = true,
     };