Update README.md

README.md

@@ -214,6 +214,14 @@ if ( intersects.length ) {
 
 _extends [TilesRendererBase](https://github.com/NASA-AMMOS/3DTilesRendererJS/blob/master/src/base/TilesRendererBase.js), which can be used to implement a 3d tiles renderer in other engines_
 
+### .fetchOptions
+
+```js
+fetchOptions = {} : Object
+```
+
+Options passed to `fetch` when loading tileset and model data.
+
 ### .errorTarget
 
 ```js