[docs] Fix links and add clarifications to docs contributing page (#23693)
[docs] Fix links and add clarifications to docs contributing page (#23693)

In the [docs contributing page](https://docs.ray.io/en/master/ray-contribute/docs.html), the links to other docs pages point to master/ instead of latest/, which can be a bit confusing since this is not the live version of the docs that people will be used to seeing.

I added a couple additional clarifications and fixed a typo as well. I also mentioned the need for an image and linked to the image directory (though some subprojects have their own image directories as well, which I did not mention).
ray-project/ray,ray-project/ray,ray-project/ray,ray-project/ray,ray-project/ray,ray-project/ray,ray-project/ray,ray-project/ray