Maildump

- Support (and require) Python 3.12

- Support Python 3 (3.6-3.9 are supported)
- Drop support for Python 2
- Use standard CSS flexbox instead of the non-standard legacy version
- Handle certain crappy emails more gracefully
- Show HTML version by default if email has HTML and text parts
- Many more fixes/improvements under the hood

- Properly handle multipart inheritance (14 - thanks jherencia)
- Fix error with python-daemon>=2.1 (17)

- Properly handle non-UTF8 emails (13 - thanks ulfrenman )

- Avoid showing 'None' as CC/BCC if the header is missing
- Handle UTF8 html emails correctly {11}

- Handle malformed MIME in a better way (thanks hansjorg)
- Show CC and BCC headers