Better documentation on marker_anchor

[jonathanng]

This documentation on creating custom markets is not very clear, especially with regards to marker_anchor.

I understand it's an array, but what do the numbers mean? Where is [0, 0]? Is that at the middle? At the bottom left (like the standard x-y axis)?

[jonathanng]

I figured this out. But I think we need to change the documentation.

[apneadiving]

With pleasure: you can update the wiki freely!