allow specific url for vertex and fragment files (not relative to root or in ShadersRepository)

src/Materials/babylon.effect.ts

@@ -178,7 +178,7 @@
 
             var vertexShaderUrl;
 
-            if (vertex[0] === "." || vertex[0] === "/") {
+            if (vertex[0] === "." || vertex[0] === "/" || vertex.indexOf("http") > -1) {
                 vertexShaderUrl = vertex;
             } else {
                 vertexShaderUrl = Engine.ShadersRepository + vertex;
@@ -209,7 +209,7 @@
 
             var fragmentShaderUrl;
 
-            if (fragment[0] === "." || fragment[0] === "/") {
+            if (fragment[0] === "." || fragment[0] === "/" || fragment.indexOf("http") > -1) {
                 fragmentShaderUrl = fragment;
             } else {
                 fragmentShaderUrl = Engine.ShadersRepository + fragment;