4.10.0 release

v4.9.4.1 release candidate (plotly#1965)

* v4.9.4.1 release candidate

* Reduce some of the warning noise

* Reduce some of the warning noise

Start v4.9.4 release candidate (plotly#1959)

Even more URL redirects

CRAN submission

bump to release version; submit to CRAN

bump version in NEWS

CRAN version v4.8.0

Also, clean up examples on help(add_trace)

bump version in NEWS

Merge pull request plotly#728 from nielsenmarkus11/nielsenmarkus11-pa…

…tch-1

Add `source` argument to both the source plot and `event_data` function