doc: add -addrinfo troubleshooting section to tor.md

Author: jonatack

doc/tor.md

@@ -15,6 +15,10 @@ There are several ways to see your local onion address in Bitcoin Core:
 You may set the `-debug=tor` config logging option to have additional
 information in the debug log about your Tor configuration.
 
+CLI `-addrinfo` returns the number of addresses known to your node per network
+type, including Tor v2 and v3. This is useful to see how many onion addresses
+are known to your node for `-onlynet=onion` and how many Tor v3 addresses it
+knows when upgrading to current and future Tor releases that support Tor v3 only.
 
 ## 1. Run Bitcoin Core behind a Tor proxy