move shaders into .glsl files and add #include feature

data/shaders/atlas.glsl

@@ -0,0 +1,21 @@
+[[vertex]]
+uniform mat4 mvp;
+uniform vec2 tof;
+uniform vec2 tsz;
+in vec2 pos;
+in vec2 uvs;
+out vec2 uv;
+void main()
+{
+   uv = tof + uvs * tsz;
+   gl_Position = mvp * vec4(pos, 0.0, 1.0);
+};
+
+[[fragment]]
+uniform sampler2D tex;
+in mediump vec2 uv;
+out mediump vec4 frag;
+void main()
+{
+   frag = texture(tex, uv);
+};