Requested documentation improvement

Tutorial workflow could be something like:

1. Define a simple game play in OpenSpiel e.g. Kuhn Poker
   • A normal form example could be easier to start
2. Set up the same game in Gambit - Is it worth developing a converter between the 2 package's Game objects?
   • In Openspiel you can do payoff_matrix = game_payoffs_array(game) and get numpy, so this would be a simple way to ineroperate between this and Gambit
3. Train agents (algorithms) in OpenSpiel to get learned strategies
4. Compare strategies of agents to Gambit's computed equilibrium strategies

OpenSpiel. notebook on colab

OpenSpiel

• In OpenSpiel, there is not a way to create arbitrary normal/extensive form games via the API or efg/nfg files as in Gambit, instead, defining a game for their library is a more involved process requiring a PR to the OpenSpiel repo, see: Call for New Games google-deepmind/open_spiel#843
  • Can you define a game manually and locally e.g. like this and register it (pyspiel.register_game(_GAME_TYPE, KuhnPokerGame)) then use it? - No, the process for adding a new game is documented here: https://openspiel.readthedocs.io/en/latest/developer_guide.html#adding-a-game
• Similar to PyGambit, there is no in-built visualiser for extensive games, however there is an external package that will do that: https://github.com/michalsustr/spielviz (which seems to be no longer maintained)
• Is there a way to list the available games from this table and filter by the thoroughly tested?