nostr-tool : Add extra fields to set_metadata subcommand
Adds an option to specify custom fields in your metadata event.
Renames update_metadata to set_metadata to make it clear that it
will simply replace your current metadata event.
https://github.com/0xtrr/nostr-tool/commit/4f1a71050b3f6cfba168fcf3c7b51d2371fe6f5d