Creates a button component for a Template message with flow button.
Honestly, I don't know what this is, the documentation only says this might be "FLOW_TOKEN" and defaults to "unused".
JSON object with the data payload for the first screen.
Protected
indexThe index of the component (assigned after calling _build)
Readonly
parametersThe parameter of the component
Readonly
sub_The subtype of the component
Readonly
typeThe type of the component
Button Component API object for flow button