Update documentation for Pod::Html and pod2html

Having been staring at https://github.com/Perl/perl5/issues/20527 for 
several weeks now and spending many hours peering into its depths, I am 
more aware than ever of the inadequacies of its documentation.

To improve the situation, I will be proposing a series of pull requests 
which will aim at things like:

* Documenting the command-line switches in lib/Pod/Html.pm and 
bin/pod2html in the same alphabetical order.

* Figuring out the best way to document the 'no*' switches.

* Having the wording of the documentation for each command-line switch 
be identical (except where that's not appropriate).

And so forth.

The first such p.r. is https://github.com/Perl/perl5/pull/20561.

If there are one or two committers who would like to be designated 
reviewers for these p.r.s, please let me know.

If there are other readers of this list who want to follow along on this 
project, please ping me.

Thank you very much.
Jim Keenan

• Update documentation for Pod::Html and pod2html by James E Keenan