Release v0.13.1

What's Changed

Mostly maintenance to support astropy 6.0 and python 3.12 while maintaining support for python 3.8

These points have changed internal behaviour, or documentation:

• Add missing return statement in private abstract class AbstractMOC in #112
• The deprecated method write now calls save internally in #117
• Add elliptical frame to some examples in #120

Full Changelog: v0.13.0...v0.13.1 and CHANGELOG.md