New user preference: Webchat position in the page

[stevetangue]

• add a new key in "preferences" object chatLocationSticky
  for location of webchat is sticky at the right or the left

• add a new key in "preferences" object chatDirectionOpen
  for direction to open bottom to top, or from the right to left or the left to right.

• add hacktober demo control radio button
  // TODO remove hacktober demo radio control

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

[dbousque]

@stevetangue Thanks, this looks really good ! @lucasdchamps can we incorporate theses changes?

[cla-assistant]

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