FR: documentation for setting up tailscale as an exit-node for proxying (ideally in userspace)

### What are you trying to do?

There doesn't seem to be good documentation on how to set up tailscale as an exit node for proxying.

Ideally in the userspce (since the owner of the machine might not want to give too much control over the machine to the proxy and want to only allow the machine to be used as an exit node.

### How should we solve this?

Provide documentation

### What is the impact of not solving this?

This can help users who might not have access to open internet for various reasons to get access to open internet.

### Anything else?

_No response_