docs: add apt and knot to EXTERNAL_PLUGINS.md (#10552)
docs: add apt and knot to EXTERNAL_PLUGINS.md (#10552)


influxdata/telegraf,nferch/telegraf,influxdata/telegraf,influxdata/telegraf,nferch/telegraf,Brightspace/telegraf,Brightspace/telegraf,nferch/telegraf,Brightspace/telegraf