Add period to end of new plugin statements in changelog

[samccann]

Fixes #87

[felixfontein]

Thanks for your contribution!

There are two aspects that should be changed:

1. This behavior should be configurable (via the config file), so collections (and ansible-core) can opt-in to this behavior;
2. The test for when to add . needs to be improved so it doesn't add periods after other punctuation; this can be done with ... description.endswith((".", ",", "!", "?"));

Also this feature needs a changelog fragment :)

[samccann]

Doing an interim push up cuz I need help. It fails CI nox tests with KeyError modules at:
https://github.com/ansible-community/antsibull-changelog/pull/162/files#diff-e5a31462878edf4ce7840f24144b38d1d878b0b6b0a0a182d8e49728e4e7aab7L429

Seems I've 'fixed it to death' and the changelog has no modules, but I'm not sure where my error is.

[samccann]

still on the todo list:

• add specific test for this
• add details to docs
• changelog fragment ;-)

[felixfontein]

Please also mention the new config file entry in docs/changelog-configuration.md.

[felixfontein]

@samccann thanks a lot for your contribution! :)

[samccann]

Thanks for all the help! This was fun :-)