virtual_sdcard: add support subdirectories in menu and M'commands

[pOmelchenko]

Added a configuration for working with subdirectories on a virtual sd card

[JamesH1978]

Thank you for submitting a PR, please could you refer to point 3 in the "what to expect" section in https://github.com/Klipper3d/klipper/blob/master/docs/CONTRIBUTING.md and add a signed-off-by line.

Thanks
James

[github-actions]

Thank you for your contribution to Klipper. Unfortunately, a reviewer has not assigned themselves to this GitHub Pull Request. All Pull Requests are reviewed before merging, and a reviewer will need to volunteer. Further information is available at: https://www.klipper3d.org/CONTRIBUTING.html

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~ Your friendly GitIssueBot

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[github-actions]

Unfortunately a reviewer has not assigned themselves to this GitHub Pull Request and it is therefore being closed. It is a good idea to move further discussion to the Klipper Discourse server. Reviewers can reach out on that forum to let you know if they are interested and when they are available.

Best regards,
~ Your friendly GitIssueBot

PS: I'm just an automated script, not a human being.