Deploy: Also deploy for tag runs?

[pat-s]

Currently we don't push in tag builds:

tic/R/steps-git.R

Lines 251 to 254 in 1228a73

	check = function() {
	!ci_is_tag()
	},

This does not play well with {fledge} and its automated release workflow since the run containing the release version (e.g. 0.3.0) is only run on a tag build (and not on a normal master push).
Hence, the pkgdown site is not deployed for this build, which leaves an automated release/version pkgdown site in an old state.

@krlmlr Is there any reason why we should not push for tag builds?

[pat-s]

ping @krlmlr