Update RenderTextureConfig.js

Author: photonstorm

src/gameobjects/rendertexture/typedefs/RenderTextureConfig.js

@@ -6,4 +6,6 @@
  * @property {number} [y=0] - The y coordinate of the RenderTextures position.
  * @property {number} [width=32] - The width of the RenderTexture.
  * @property {number} [height=32] - The height of the RenderTexture.
+ * @property {string} [key] - The texture key to make the RenderTexture from.
+ * @property {string} [frame] - the frame to make the RenderTexture from.
  */