Update README.md

README.md

@@ -8,6 +8,7 @@ A very small C library for putting pixels on the screen, perfect for software ra
 - [x] Win32 (Windows)
 - [x] Wayland (Linux):  
       Wayland development packages are needed for building (for example on Ubuntu: `sudo apt install libwayland-dev wayland-protocols`), you also need a running Wayland session at runtime.
+      You also need pkg-config `sudo apt install pkg-config`.
 - [x] X11 (Linux and macOS):  
       * **Linux**: X11 development packages are needed for building (for example on Ubuntu: `sudo apt install libx11-dev`), you also need a running X11 session at runtime.  
       * **macOS**: [XQuartz](https://www.xquartz.org/) is needed at runtime.