DOC: Add Pandas-Bokeh to pandas ecosystem page
This PR adds Pandas-Bokeh reference to Pandas ecosystem page. 

Best, Patrik
Docs look good.  I would merge / rebase with `master` to re-trigger the CI. > Docs look good. I would merge / rebase with master to re-trigger the CI.

The docs and checks CI builds are passing, so a re-trigger is not needed I think. Thanks @PatrikHlobil ! (and also thanks for working on the pandas-bokeh package!) @jorisvandenbossche : Thanks for reviewing this PR so fast and also thanks for working on Pandas ;)