Use sphinx-changelog

[maxnoe]

Replace custom solution with using sphinx-changelog, this also works on readthedocs and means we get the changelog previewed in the "latest" docs.

[Tobychev]

Results look identical between the CI version and latest, so I'm confused about what you mean by this "we get the changelog previewed"?

I can spot one behaviour change between the CI version and prod: when you scroll all the way up on the CI the right hand side content menu doesn't collapse down to one line per release like it does on prod.

[maxnoe]

Results look identical between the CI version and latest,

That's because we haven't merged anything yet since the last tag

[Tobychev]

I tried rerunning the docs build now that the Astropy 7 PR got merged but again I can't see anything being picked up... though github itself is not picking up #2639 in the "is:pr is:closed" view either?

[maxnoe]

But this branch is not updated with respect to main

[maxnoe]

You can now see it here: https://ctapipe.readthedocs.io/en/latest/changelog.html @Tobychev