Mail-deduplicate

- Build standalone executable for macOS, Linux and Windows.
- Generates dependency graph in Graphviz format.
- Run tests on Python `3.12-dev`.
- Code, comments and documentation style change to conform to new QA workflows based on `ruff`.

- Renumber and rename phases to steps.
- Group options per steps.
- Add minimal code typing and checking.
- Add logo.
- Execute all workflows with Python 3.11.

- Drop Python 3.6 support.
- Add support for Python 3.11.
- Add new `--time`/`--no-time` option to measure elapsed execution time.
- Add new `--color`/`--no-color` and `--ansi`/`--no-ansi` alias options to deactivate CLI color rendering.
- Add new `--color`/`--no-color` and `--ansi`/`--no-ansi` alias options to deactivate CLI color rendering.
- Add new `-C`/`--config` option which support local and remote configuration file in TOML, YAML, JSON, INI or XML formats.
- Add new `--show-params` option to debug default parameter value and provenance.
- Fix incconsistent printing of help screen. Closes {issue}`160`.
- Force linear rendering of options in help screen to improve readability.
- Fix run on Python 3.10. Closes {issue}`361`.
- Run unittests on Python 3.10 and Python 3.11.
- Add dependency on `click-extra` and `typing-extensions`
- Remove direct dependency on `click-help-colors`, `click-log` and `tomlkit`.
- Fix broken selection logic in quantity-based strategies. Refs {issue}`146`.
- Add unittests to cover time-based and size-based selection edge-cases.
- Drop unittests on deprecated `ubuntu-18.04` and `macos-10.15`.
- Add unittests on `ubuntu-22.04`, `macos-12` and `windows-2022`.
- Run tests on multiple cores.
- Simplify project management by abandoning the dual use of `main`/`develop` branches.
- Migrate to external workflows to automate builds, releases, autofixes, linting, documentation, changelog, mailmap maintenance and label management.
- Convert all documentation from RST to Markdown. Closes {issue}`368`.
- Keep CLI output in sync in documentation. Closes {issue}`23`.
- Move `sphinx` dependencies to dev requirements.
- Add citation file.

- Upgrade to Click 8.x.
- Implements all missing `copy-discarded`, `move-discarded` and
`delete-discarded` actions. Closes {issue}`270` and {issue}`146`.
- Add `-b`/`--hash-body` option to set the way each email body is
hashed.
- Add `--export-append` option to allow for the resulting deduplicated
email to be appended to an existing mail box.
- Skip duplicate sets without any matching duplicate candidates. Closes
{issue}`203`.

- Fix dynamic `mailbox.Message` inheritance. Closes {issue}`191`.

- Reconcile `v3` branch with `develop`.