move shaders into .glsl files and add #include feature

data/shaders/color-quad.glsl

@@ -0,0 +1,20 @@
+[[vertex]]
+uniform mat4 mvp;
+in vec4 pos;
+in vec2 uvs;
+out vec3 uv;
+void main()
+{
+   gl_Position = mvp * pos;
+   uv = vec3(uvs, pos.w);
+};
+
+[[fragment]]
+#include "include/hsv.glsl"
+uniform mediump vec4 col; // HSV
+in mediump vec3 uv;
+out mediump vec4 frag;
+void main()
+{
+    frag = vec4(hsv2rgb(vec3(col.x, uv.x, 1.0 - uv.y)), 1.0);
+};