Outgoing

-------------------
- Support Python 3.10
- Replaced `entrypoints` dependency with `importlib-metadata`
- Replaced `appdirs` dependency with `platformdirs`. This is a **breaking**
change on macOS, where the default configuration path changes from
`~/Library/Application Support/outgoing/outgoing.toml` to
`~/Library/Preferences/outgoing/outgoing.toml`.

-------------------
- `outgoing.errors.UnsupportedEmailError` is now re-exported as
`outgoing.UnsupportedEmailError` like all the other exception classes

-------------------
- Update for tomli 1.2.0

-------------------
- Read TOML files in UTF-8

-------------------
- Switch from toml to tomli

-------------------
- Support Click 8