Add existing to tracked

node_modules/@cesium/engine/Source/Shaders/SkyBoxFS.glsl

@@ -0,0 +1,9 @@
+uniform samplerCube u_cubeMap;
+
+in vec3 v_texCoord;
+
+void main()
+{
+    vec4 color = czm_textureCube(u_cubeMap, normalize(v_texCoord));
+    out_FragColor = vec4(czm_gammaCorrect(color).rgb, czm_morphTime);
+}