Update tokens.md to add new section, "Replacing tokens in non-ECA actions."

docs/eca/concepts/tokens.md

@@ -186,3 +186,8 @@ entities will cause similar issues.
 
     In ECA 2.0 there is an option to force token replacement to plain text only. By default, token replacement remains
     the same as it is implemented in Drupal core, so that your model only changes behaviour intentionally.
+
+
+### Replacing tokens in non-ECA actions
+
+Action plugins that are not developed specifically for ECA often do not contain a token-replace function, and therefore may not automatically replace any tokens that are passed into them. Those action plugins (for example, "send mail" and "display message to user" and others listed under "Drupal core" in the task's "Choose element template" dialog) will have a "Replace tokens" field at the bottom of their configuration panes. Setting that field to "yes" may be necessary for proper token replacement. Tip: If you're having trouble with token replace in an action plugin, and the "Replace tokens" field is visible and set to "no," try changing it to "yes" as a first step in debugging.