New user preference: Webchat position in the page

[janteuni]

Add a new key in "preferences" object to choose if the webchat is sticky at the right or the left of the page. And if the Webchat opens like now from the bottom to top, or from the right to left / or the left to right.

[stevetangue]

Hi @janteuni, hope it is ok, looked into this one and gave it a go. happy to hear your recommendation and feedback. https://github.com/SAPConversationalAI/Webchat/pull/42

demo https://stevetangue.github.io/chatpage/