Update links at the Vanity Addresses page

Description

Vanity Addresses page needs updated links/references.

Specifically, these references are outdated:

• eotk/docs.d/TIPS-FOR-MINING-ONIONS.md at master · alecmuffett/eotk
• Onion Services UX Proposals · Wiki · The Tor Project / Onion Services / Onion Support · GitLab

And can be replaced by:

• Mining Onion Service keys - Onionspray
• Usability intro - The Onion Plan

A reference to Onionmine would also be informative.

Tasks

• Replace the oudated references with the newer ones.
• Add a reference to Onionmine.

Time estimation

• Complexity: negligible (0.1 day)
• Uncertainty: low (x1.1)
• Reference (adapted)