Map shader base, add memory util.

src/duskgl/display/shader/fragments/quad.glsl

@@ -3,6 +3,14 @@
 // This software is released under the MIT License.
 // https://opensource.org/licenses/MIT
 
+uint quadGetIndiceIndex(uint vertexId) {
+  return vertexId % 6u;
+}
+
+uint quadGetIndiceIndex(int vertexId) {
+  return quadGetIndiceIndex(uint(vertexId));
+}
+
 vec2 quadGetVertice(uint indiceIndex) {
   vec2 vert = vec2(0, 0);