Clarifications on pkgdown workflows

[maelle]

@krlmlr reg #1064 to follow https://pkgdown.r-lib.org/dev/articles/how-to-update-released-site.html I need some clarifications.

• we need a workflow dispatch: do I add it to https://github.com/cynkra/dm/blob/main/.github/workflows/pkgdown.yaml

[maelle]

To make the workflow dispatch able to replace the released website do you agree we need to replace the lines

if: github.event_name != 'push'

with

if: github.event_name != 'pull_request'

[krlmlr]

The pkgdown deployment workflow should be triggered for all branches named docs* ?