Add Order Independent Transparency example (#755)

* Add Order Independent Transparency example

* Update README.md

* Add copyright at Order Independent Transparency example

* Disable the validation by default

data/shaders/glsl/oit/geometry.frag

@@ -0,0 +1,49 @@
+#version 450
+
+#define MAX_FRAGMENT_COUNT 75
+
+layout (early_fragment_tests) in;
+
+struct Node
+{
+    vec4 color;
+    float depth;
+    uint next;
+};
+
+layout (set = 0, binding = 1) uniform ObjectUBO
+{
+    mat4 model;
+    vec4 color;
+} objectUBO;
+
+layout (set = 0, binding = 2) buffer GeometrySBO
+{
+    uint count;
+    uint maxNodeCount;
+};
+
+layout (set = 0, binding = 3, r32ui) uniform uimage2D headIndexImage;
+
+layout (set = 0, binding = 4) buffer LinkedListSBO
+{
+    Node nodes[];
+};
+
+void main()
+{
+    // Increase the node count
+    uint nodeIdx = atomicAdd(count, 1);
+
+    // Check LinkedListSBO is full
+    if (nodeIdx < maxNodeCount)
+    {
+        // Exchange new head index and previous head index
+        uint prevHeadIdx = imageAtomicExchange(headIndexImage, ivec2(gl_FragCoord.xy), nodeIdx);
+
+        // Store node data
+        nodes[nodeIdx].color = objectUBO.color;
+        nodes[nodeIdx].depth = gl_FragCoord.z;
+        nodes[nodeIdx].next = prevHeadIdx;
+    }
+}