Add list of possible container states to docker docs (influxdata#6099)

Author: kden416

plugins/inputs/docker/README.md

@@ -32,6 +32,8 @@ to gather stats from the [Engine API](https://docs.docker.com/engine/api/v1.24/)
 
   ## Container states to include and exclude. Globs accepted.
   ## When empty only containers in the "running" state will be captured.
+  ## example: container_state_include = ["created", "restarting", "running", "removing", "paused", "exited", "dead"]
+  ## example: container_state_exclude = ["created", "restarting", "running", "removing", "paused", "exited", "dead"]
   # container_state_include = []
   # container_state_exclude = []
 

plugins/inputs/docker/docker.go

@@ -96,6 +96,8 @@ var sampleConfig = `
 
   ## Container states to include and exclude. Globs accepted.
   ## When empty only containers in the "running" state will be captured.
+  ## example: container_state_include = ["created", "restarting", "running", "removing", "paused", "exited", "dead"]
+  ## example: container_state_exclude = ["created", "restarting", "running", "removing", "paused", "exited", "dead"]
   # container_state_include = []
   # container_state_exclude = []