Separated color passes into separate modules.

Moved main JS into its own module.
Main module now builds passes into a pipeline, based on the value of config.effect.
The passes no longer make stubs when they're not meant to be active.
Asset loading has been moved into the passes, which resolve their ready promise when they've finished loading.

js/stripePass.js

@@ -0,0 +1,37 @@
+import { makePassFBO, makePass } from "./utils.js";
+
+export default (regl, {}, input) => {
+  const output = makePassFBO(regl);
+  return makePass(
+    output,
+    regl({
+      frag: `
+      precision mediump float;
+      #define PI 3.14159265359
+
+      uniform sampler2D tex;
+      uniform sampler2D stripes;
+      uniform float ditherMagnitude;
+      varying vec2 vUV;
+
+      highp float rand( const in vec2 uv ) {
+        const highp float a = 12.9898, b = 78.233, c = 43758.5453;
+        highp float dt = dot( uv.xy, vec2( a,b ) ), sn = mod( dt, PI );
+        return fract(sin(sn) * c);
+      }
+
+      void main() {
+        vec3 color = texture2D(stripes, vUV).rgb - rand( gl_FragCoord.xy ) * ditherMagnitude;
+        float brightness = texture2D(tex, vUV).r;
+        gl_FragColor = vec4(color * brightness, 1.0);
+      }
+    `,
+
+      uniforms: {
+        tex: input,
+        ditherMagnitude: 0.1
+      },
+      framebuffer: output
+    })
+  );
+};