New sample config for snippet-box

[paroxy777]

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• I have read the contributing guideline and understand that I have made the correct modifications

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Description

Adds new sample config for snippet-box

Benefits of this PR and context

Including sample proxy configs helps new users to get started with SWAG

How Has This Been Tested?

Testing environment:
UnRAID's built-in Docker implementation with SWAG and snippet-box containers installed.

Testing Details:

• configured DNS with new CNAME for new subdomain
• configured SWAG to with new subdomain
• renewed SSL cert
• added the new proxy subdomain config for snippet-box
• can now access snippet-box on port 443 using the new subdomain, both locally and remotely.

Source / References

https://github.com/pawelmalak/snippet-box