Add bots.handle_draw_offers and bots.handle_takeback_offers

[FriedrichtenHagen]

Checklist when adding a new endpoint

• Added new endpoint to the README.md

• Ensured that my endpoint name does not repeat the name of the client. Wrong: client.users.get_user(), Correct: client.users.get()

• Typed the returned JSON using TypedDicts in berserk/types/, example
  I did not type the returned json since it is not typed in other bots endpoint methods. The response is quite minimal ({
  "ok": true
  }). I could add this (also for the other bot endpoints) if desirable.

• Written tests for GET endpoints not requiring authentification. Documentation, example
  These endpoints require authentication.

• Added the endpoint and your name to CHANGELOG.md in the To be released section (to be created if necessary)