fix: Create config file if it does not exist

[dbolson]

When running a command, if there isn't a config file then create one. Since most users will not want to specify their access token, etc. for each command, we can assume they will want a config file.

If we can't write the config file, fail silently. Then when running any config commands, the error will give more details.

You can test this by deleting or moving the ~/.config/ldcli/config.yml file and running ldcli config --list.

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• I have added test coverage for new or changed functionality
• I have followed the repository's pull request submission guidelines
• I have validated my changes against all supported platform versions

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