Add missing direct Perl dependency TimeDate for command genhtml

[hartwork]

Side product of https://bugs.gentoo.org/947646 …

Not to be confused with DateTime 😃 (which did happen to me)

# git --no-pager grep Date::Parse
bin/genhtml:use Date::Parse;
bin/genhtml:            my $epoch = Date::Parse::str2time($baseline_date);

https://metacpan.org/pod/Date::Parse

[henry2cox]

Can you go ahead and add a 'Signed-off-by' field to the PR comment?
I think we need that before merging. (Yeah - pedantic. Sorry.)

[hartwork]

@henry2cox no worries, it's been a while since my last commit here. git rebase --signoff master did all the work for me, done, pushed.