Add Tailscale reverse proxy example to README

[thatwonguy]

Closes #823. Relates to #341.

Adds a Tailscale configuration example to the "Example configurations" section of the reverse proxy documentation, covering the CGNAT use case for users hosting ESS for a private group of friends or family.

The example covers:

• Prerequisites: tailnet membership for all users, domain name, DNS01 cert-manager challenge (required since port 80 is not publicly reachable)
• Tailscale install steps
• Nginx and Caddy configs bound to the Tailscale interface

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[gaelgatelement]

Hello,

Thank you for your suggestion !

Why didn't you go with setting up tailscale in the k3s cluster, and profit from https://tailscale.com/docs/features/kubernetes-operator/how-to/cluster-ingress ?

This section being dedicated to external proxies, it seems a bit strange to mention tailscale in this context. It feels like it should be documented as an option in nginx/caddy configuration instead, where you would bind to specific addresses instead of all ips.

We'd be willing to take your contribution if you refactored the documentation accordingly.

Remember to sign the CLA to allow us to merge your contribution if you push forward.

Thanks!