Add position field to tooltip.js doc
Add position field to tooltip.js doc

The next PR merged in 2016 show the addition of the position field but was not added to the doc.
https://github.com/recharts/recharts/commit/31d2b2d367adecaef34c5bb0371f27126dc51d8b

I spent 20mins to find it 😅😅
I think it might be useful to many :-) 

I did the chinese translation on google translate, improve it if not accurate please
recharts/recharts.org,recharts/recharts.org