Added hint button, need to add functionality.

[ItsDang]

For #1158

[CloudyDino]

Hey @ItsDang! Did you want any help closing this out? Looks like the things left are:

• Using a green circle for the hint piece
• Adding hintShown to PuzzleState and setting it to true if we're toggling the hint to show
• Setting the puzzle solution's rated parameter to initialContext.userId != null && !state.hintShown
• Checking if it's possible to preselect the piece the move is from instead of circling all those valid moves (Honestly, I'm not sure how to do this part)

[ItsDang]

Hey @CloudyDino, I'll try to get it fixed with the tests tomorrow, but feel free to work on it :) Thanks for adding the comment about the rated param 👍

[ItsDang]

Reopened to check if my changes would pass the tests, mainly to check if the save formatting passed, the dart format command from contribution isn't working for me? Going to close, please merge @CloudyDino's #1459 instead 😄.