Fix: `cruft diff` fails for `cookiecutter` local extensions (cruft#290)

* Fix diff UnknownExtension: Handle directory like update is doing

* tests: Add check and diff

* Apply reformat

* add tests to fullfil coverage requirements

* fix format

* remove unused extension

* Re-format files

* Use appropriate fixtures and update to cruft repo

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Co-authored-by: Fabian Todt <[email protected]>
Co-authored-by: Sambhav Kothari <[email protected]>

Update Dockerfile to reference latest python image

Preempt tests on updates (cruft#328)

Update CHANGELOG.md (cruft#249)

Update CHANGELOG.md

Update CHANGELOG.md

Update changelog in preperation for 2.12.0 release

Update CHANGELOG.md

Update CHANGELOG.md

Update changelog