Integrate prop351 into socks-extensions.md, and mark it as closed.

Now that it's implemented in Tor and Arti, it's proper to make this part of the spec per se rather than a proposal.

The text here is copied directly from proposal 351, per its instructions.

Note that the section about A further extension for integration with Arti SOCKS is going into the arti docs for now.

assigned to @nickm

requested review from @ahf

added 1 commit

• 8c61af66 - socks-extensions: fix a link.

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mentioned in merge request arti!2474 (merged)

mentioned in issue arti#1615 (closed)

approved this merge request

Looks good

merged