Adds a info box describing invalid property or trait values in actions

Author: nick-Ag

src/connections/destinations/actions.md

@@ -212,6 +212,10 @@ Mapping fields are case-sensitive. The following type filters and operators are
     You can specify nested properties using dot notation, for example `context.app.name`. If the property might appear in more than one format or location, you can use an ANY statement and add conditions for each of those formats. For example, you might filter for both `context.device.type = ios`  as well as `context.os.name = "iPhone OS``"`
     The `does` `not exist` operator matches both a `null` value or a missing property.
 {% comment %}
+
+> info "Valid Property and Trait Values"
+> Property or trait names must begin with the characters: [a-z], [A-Z] or '_'. Special characters are unsupported and will trigger an error if entered.
+
 > info "Event property operators and supported data types"
 > Operators support matching on values with a **string** data type:
 > - `is`, `is not`, `contains`,  `does not contain`, `starts with`, `ends with`