Documented support for wild card thing status triggers (openhab#2438)

openhab/openhab-core#2832 added support for wild card Thing status triggers. This PR adds a couple of sentences documented that and how to use it.

Signed-off-by: Richard Koshak <[email protected]>

Author: rkoshak

configuration/rules-dsl.md

@@ -277,6 +277,8 @@ You can find all the possible values for status from [Thing Status](/docs/concep
 The `thingUID` is the identifier assigned to the Thing, manually in your configuration or automatically during auto discovery.
 You can find it from UI or from Karaf remote console.
 For example, one z-wave device can be "zwave:device:c5155aa4:node14".
+The `*` wildcard is allowed in the `thingUID`.
+For example, `chromecast:*` will trigger on all `chromecast` Things and `*` will trigger on all things.
 
 If the Rule needs to know what the triggering thing was, or access a string value of the previous or new status, use the [implicit variables]({{base}}/configuration/rules-dsl.html#implicit-variables-inside-the-execution-block) `triggeringThing`, `previousThingStatus` or `newThingStatus` to access the information.