Flowbuilder: Custom placeholder in message field

Feature Request Summary: 

It should be possible to change the placeholder text in the message field in Flowbuilder/Messaging Widget

Description/Use Cases: 

In some cases when a messaging widget is started with a Flowbuilder, the default placeholder in the input field is encouraging the end user to type in some free text. This is inappropriate if the Flowbuilder relies on the end user to click through the Flow and not rely too much on the intents added to the answer. This might leave the end user with a bad first experience with the Flowbuilder.

Adding a custom placeholder will enable us to encourage the end user to click through the Flow if this is the intention.

There are many options as I see it, that would help with this challenge.

- Being able to define the placeholder text, via. script settings like in Classic Web widget, or having the setting in the Widgets settings page in Zendesk admin.
- Being able to hide the message field when in a Flowbuilder, and not show it before a handover has been done/started

The business impact of limitation or missing feature:

As stated above, when a Flowbuilder is heavily relying on click instead of free text search, for what ever reason, the end user will have a bad experience if there is a high chance of the Flowbuilder not understanding the free text input.

Other necessary information or resources:

https://www.pizzahut.com/