Add chat on irc badge (#2214)

* Add chat on irc badge

As it is the channel with more maintainers in

* Correct url id

* More corrections





* Add a contact header

To make it more visible in indices

Co-authored-by: Pepe Iborra <pepeiborra@gmail.com>
Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>