DOC: reference the visualization page from the ecosystem one
The link already exists in the other direction, so want to make sure readers who come across the latter understand the built-in option.

- [ ] ~~closes #xxxx~~
- [ ] ~~tests added / passed~~
- [ ] ~~passes `black pandas`~~
- [ ] ~~passes `git diff upstream/master -u -- "*.py" | flake8 --diff`~~
- [ ] ~~whatsnew entry~~
