Update the docs reference for textureWidth/textureHeight

[Roi Peker]

When using in nodeJS, options.textureWidth/options.textureHeight doesn't work, looking at index.js seems the actual value is options.textureSize...
Maybe update index.js to have granular access to width/height, or README to reflect the correct prop name.

Update:
just realized .textureSize expected an array of [width,height], please update the README.

[Shen Yiming]

Thanks for the report! node module is less used and doc does not reflect new changes.

[Shen Yiming]

Fixed via 67cd028