Typo in Documentation: Conventions

[mosesintech]

Actual Result

Excalibur uses [Resources](https://excaliburjs.com/docs/docs/category/resources) to load external files like [images](https://excaliburjs.com/docs/ImageSource) and [sounds](https://excaliburjs.com/docs/Sound). They can also be used to load other things like data or config.

The Resources link is missing the preceding / resulting in a 404.