move shaders into .glsl files and add #include feature

data/shaders/lambert.glsl

@@ -0,0 +1,23 @@
+[[vertex]]
+uniform mat4 mvp;
+in vec4 pos;
+in vec3 nor;
+in vec2 uvs;
+out vec3 n;
+void main()
+{
+   n = nor;
+   gl_Position = mvp * pos;
+}
+
+[[fragment]]
+uniform mediump vec3 light_dir;
+uniform mediump float ambient;
+in mediump vec3 n;
+out mediump vec4 frag;
+void main()
+{
+    mediump float d = max(0.0, dot(normalize(n), light_dir));
+    frag = vec4(vec3(d) + ambient, 1.0);
+    //frag = vec4(normalize(n) * 0.5 + 0.5, 1.0);
+}