move shaders into .glsl files and add #include feature

data/shaders/bake-uv.glsl

@@ -0,0 +1,27 @@
+[[vertex]]
+uniform mat4 mvp;
+in vec4 pos;
+in vec3 nor;
+in vec2 uvs;
+out vec3 n;
+out vec3 p;
+void main()
+{
+    n = nor;
+    p = vec3(mvp * pos);
+    gl_Position = vec4(uvs * 2.0 - 1.0, 0.0, 1.0);
+}
+
+[[fragment]]
+uniform int mode;
+in highp vec3 n;
+in highp vec3 p;
+out highp vec3 frag;
+void main()
+{
+    switch(mode)
+    {
+    case 0: frag = normalize(n); break;
+    case 1: frag = p; break;
+    }
+}