reorganize to use .bat files instead of .sh. Move demo to an example project

assets/shaders/fragment.glsl

@@ -0,0 +1,16 @@
+#version 330 core
+
+uniform vec4 color;
+
+in vec3 frag_pos;
+
+out vec4 frag_color;
+
+void main() {
+    vec3 dx = dFdx(frag_pos) * 500;
+    vec3 dy = dFdy(frag_pos) * 500;
+    vec3 N = normalize(cross(dFdx(frag_pos), dFdy(frag_pos)));
+    frag_color = color;
+    //frag_color = vec4(length(dx), length(dy), length(dy), 1.0);
+    //frag_color += color;
+}