Update custom-audiences.md (#522)

added link to the recording

docs/workflow/implementing/custom-audiences.md

@@ -16,7 +16,7 @@ They are:
 
 ### How to add a new custom audience
 
-Create a PR against [targeting/constants.py](https://github.com/mozilla/experimenter/blob/main/experimenter/experimenter/targeting/constants.py) that adds a new JEXL expression.
+Create a PR against [targeting/constants.py](https://github.com/mozilla/experimenter/blob/main/experimenter/experimenter/targeting/constants.py) that adds a new JEXL expression.  There is a [recorded session showing 2 examples of adding custom targeting](https://mozilla.hosted.panopto.com/Panopto/Pages/Viewer.aspx?id=8527feae-303e-41b3-b9df-b0a800f3cd41) to demoonstrate where to start.
 
 Request review from a console core team member. It should be available in the Experimenter UI a few minutes after the PR has merged.
 
@@ -30,4 +30,4 @@ New custom audiences should be tested by the core Nimbus team before they are us
 - Test the whole JEXL expression on each application/device it is intended to run on.
 - Ask QA to help verify it by creating a dummy experiment.
 - Launch an A/A in nightly to see if real users enroll correctly
-:::
+:::