Releases timeline app

[droumis]

We received feedback in the user survey to add some information to the release pages for anticipated release timelines. I am not sure that we want to tie ourselves to a specific future timeline, but perhaps instead we could display a timeline plot of past releases to give people some anticipation of actual release frequency (major, minor, etc).

I am not sure if such an app should live on the individual release pages of HoloViz core projects, or if it could be linked from there and live on this status dashboard repo, where we could include a link to the app for each row of the core packages.