Rework Credits section slightly
Rework Credits section slightly

Put Authors, Contributors, Maintainers, Other Credits
as subsections of Credit.

Yajo/maintainer-tools,OCA/maintainer-tools,acsone/maintainers-tools,acsone/maintainer-tools,Yajo/maintainer-tools,Yajo/maintainer-tools,OCA/maintainer-tools,OCA/maintainer-tools,Yajo/maintainer-tools,acsone/maintainer-tools,acsone/maintainers-tools,acsone/maintainer-tools,acsone/maintainer-tools,acsone/maintainers-tools,OCA/maintainer-tools