Adds coordinate scaling to fix max-width issue.

When using large images the current DokuWiki default template automatically scales the image to `max-width: 100%`. Unfortunately, this makes large image maps unusable because the clickable areas aren't scaled together with the image.

This can be fixed by scaling the image map itself as well. This fix is based on @stowball's https://github.com/stowball/jQuery-rwdImageMaps.