Added raymarch example and thumbnail for write depth (#2919)

examples/shaders/resources/shaders/glsl100/hybrid_raster.fs

@@ -0,0 +1,16 @@
+#version 100             
+#extension GL_EXT_frag_depth : enable   // Extension required for writing depth         
+precision mediump float;                // Precision required for OpenGL ES2 (WebGL)
+
+varying vec2 fragTexCoord;
+varying vec4 fragColor;
+
+uniform sampler2D texture0;
+uniform vec4 colDiffuse;
+
+void main()
+{
+    vec4 texelColor = texture2D(texture0, fragTexCoord);
+    gl_FragColor = texelColor*colDiffuse*fragColor;
+	gl_FragDepthEXT = gl_FragCoord.z;
+}