Update script Rock Paper Scissors to refelct reallity in the rule base

[bbob122]

The script Rock Paper Scissors is a great way to spend some spare time, for instance during classes. However, the current implementation would benefit from some improvements I would like to add:

1. Currently the implementation does not allow a draw between the computer and the human. This is not really reflecting how the game works.
2. There are some inconsistencies in capitalisation of user outputs
3. There is no error handling when the user is asked if he would like to continue, i.e. also a "No" will start a new round
4. The readme.md file needs to be updated.

@DhanushNehru Could you please assign the Issue to me?