Guess the move

These are the ideas to tickets #2 and #92

What are the things that have to be changed for that functionality:

• A kind of view mode, but with editing functionality (only pre-defined moves) ✔️
• Only show already guessed moves, hide the not-guessed ones ✔️
• Have some additional text displayed as initial question / question per move / feedback to the guesser
  • questions per move could be included in the moves themselves as a comment
• Possibility to get help ✔️

There is no supporting format in PGN for guessing a move, but we may use comments to get something similar.

The change to the UI would be the following:

• Add to the view buttons a "?" button to get help. The button "Go to next move" could be used instead.
• Add to the view buttons a button for solving (have to find the right icon). The button "Go to last move" could be used instead.
• Add a text line below / above the buttons to allow feedback to the player.
• Add a help text above the whole board (that can be hidden then) that explains how to play that puzzle.

Change in algorithm:

• Know what the current state is, that means up to which move the puzzle is solved. Change the buttons nextMove and lastMove accordingly.
• Use the buttons nextMove and lastMove to show the next / all moves instead.
  • Give some feedback, that the move is shown, and was not guessed.
• React on each played move by
  • displaying that the move was wrong (something like "not the best move, try another one") and taking the move back. ✔️
  • giving applause to the move ✅
• React on the last move to play, that the solution was found (something like "you found the solution for the puzzle").
• The feedback given has to be internationalized, and may be an additional parameter of the configuration.
• The PGN given are only the valid moves, no variations allowed. ✔️
• There has to be set an initial position, from where to start the puzzle. ✔️
• All moves are initially hidden (display: none), and after successful move only shown. So the rendering of the move list has not to be changed. ✔️