Add 'best' game piece

Chooses the best game piece based on proximity to (x, y) cordinates.

Signed-off-by: Filip Kujawa <filip.j.kujawa@gmail.com>
Change-Id: I67ddbd749137e95b99a1d215373aeb044c949667
diff --git a/y2023/vision/game_pieces.fbs b/y2023/vision/game_pieces.fbs
index e981712..773cc93 100644
--- a/y2023/vision/game_pieces.fbs
+++ b/y2023/vision/game_pieces.fbs
@@ -8,8 +8,8 @@
 }
 
 // Bounding box dimensions and position.
+// X and Y represent the top left of the bounding box.
 table Box {
-    //TODO(Filip): Are cords center of box or top left corner?
     x:uint (id: 0);
     y:uint (id: 1);
     w:uint (id: 2);
@@ -24,6 +24,7 @@
 
 table GamePieces {
     game_pieces:[GamePiece] (id: 0);
+    best_piece:uint (id: 1); // Index of the "best piece".
 }
 
 root_type GamePieces;
\ No newline at end of file