w3c/groups: auto-update list of working groups

[iherman]

Description of problem

The list of the groups managed by Respec has not been updated. It still lists the EPUB WG (which has been closed) and does not include the Publishing Maintenance WG (which has just started).

URL to affected page:

https://respec.org/w3c/groups/

cc @deniak

[iherman]

cc @mattgarrish

[sidvishnoi]

I've manually run update script on server. Keeping this issue open to automate it in future.