add fragment shader

src/shaders/vertex.glsl

@@ -0,0 +1,9 @@
+#version 330 core
+layout (location = 0) in vec2 aPosition;
+
+out vec3 vertexColor;
+
+void main() {
+	vertexColor = vec3(1.0, 0.0, 0.0);
+	gl_Position = vec4(aPosition, 0.0, 1.0);
+}