Sopel 8 will support SASL EXTERNAL / CertFP

x-ref: sopel-irc/sopel#2100

Author: dgw

_data/sw_clients.yml

@@ -1080,4 +1080,5 @@
           server-time: "6.2.0+"
           userhost-in-names: "8.0.0+"
         SASL:
-          - plain
+          plain: "4.1.0+"
+          external: "8.0.0+"