Updated Iptables reverse proxy documentation to include support for unix domain sockets

[pyther-hub]

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This is a simple documentation change that I have done for this issue #6895 I have added

Adding Unix Domain Sockets Support What does Unix Domain Sockets Support Mean for Iptables? and the Example Configuration:

I am fairly new to making open source contribution but I read the guidlines and I hope I have not done anything wrong please do let me know