Implement behind feature flag
 Add a new parameter property to TemplateData, called 'suggestedvalues' in JSON. //Note: on test instance this was titled datalist. We want to make sure that the naming is consistent in the final implementation.//
 Add field to edit this new property in the TemplateData editor on the parameter properties page underneath the type property. For input, use OOUI TagMultiselectWidget (allowArbitrary, inline input, placeholder). The items can then also include commas.
 Give this field a label of: "Suggested values"
 Only have this property visible when the following parameter types are selected: Content, Line, String, Unknown, Number, File, Page, Template. Otherwise, hide the property and its field.
 Placeholder text: "Add value..."
Relevant prototype commits: