Configuration files are checked in this order:
1. CLI argument
2. `$MOBILIZION_RESHARE_SETTINGS_FILE` environment variable;
3. User configuration directory. On Linux that's `$XDG_CONFIG_HOME/mobilizon_reshare/<mobilizon-reshare-version>`;
4. System configuration directory. On Linux that's the first element in `$XDG_CONFIG_DIRS` + `/mobilizon_reshare/<mobilizon-reshare-version>`.
5. The default configuration distributed with the package.
The first available configuration file will be loaded. Secrets can be set either
via environment variables (such as `export MOBILIZON_RESHARE_PUBLISHER_TELEGRAM_TOKEN="my-telegram-token"` )
or by setting the `$SECRETS_FOR_DYNACONF` environment variable to a `secrets.(toml|yaml|ini|json)` file.
Co-authored-by: Giacomo Leidi <goodoldpaul@autistici.org>