fix for rivers and bridges snake start positions (#85)

* fix for rivers and bridges snake start positions

* update max player count, add unit test

* set player count to 12 (max for smallest size)

* fix: one of the 19x19 spawn points

* randomize snake placement at start positions

* randomly choose starts in quadrants

* fix: check that start positions are valid

* modify food placement to avoid hazards

maps/hazards_test.go

@@ -103,13 +103,13 @@ func TestRiversAndBridgetsHazardsMap(t *testing.T) {
 	// check all the supported sizes
 	for _, size := range []int{11, 19, 25} {
 		state = rules.NewBoardState(size, size)
+		state.Snakes = append(state.Snakes, rules.Snake{ID: "1", Body: []rules.Point{}})
 		editor = maps.NewBoardStateEditor(state)
 		require.Empty(t, state.Hazards)
 		err = m.SetupBoard(state, settings, editor)
 		require.NoError(t, err)
 		require.NotEmpty(t, state.Hazards)
 	}
-
 }
 
 func TestSpiralHazardsMap(t *testing.T) {