example: defines GLAD_GL_IMPLEMENTATION in GLFW example (#464)

Author: makichiis

.gitignore

@@ -17,4 +17,5 @@ dist/
 /glad-rs/
 /rust/
 target/
-Cargo.lock
+Cargo.lock
+.vscode/

example/c/gl_glfw.c

@@ -1,6 +1,7 @@
 #include <stdlib.h>
 #include <stdio.h>
 
+#define GLAD_GL_IMPLEMENTATION // Necessary for headeronly version.
 #include <glad/gl.h>
 
 #include <GLFW/glfw3.h>