Fix yaw out of bounds in mouseEventToCoords

If config.yaw is close to -180 or 180, yaw might be out of bounds.

src/js/pannellum.js

@@ -704,6 +704,8 @@ function mouseEventToCoords(event) {
     var root = Math.sqrt(x*x + a*a);
     var pitch = Math.atan((y * c + focal * s) / root) * 180 / Math.PI;
     var yaw = Math.atan2(x / root, a / root) * 180 / Math.PI + config.yaw;
+    if (yaw < -180) yaw += 360;
+    if (yaw > 180) yaw -= 360;
     return [pitch, yaw];
 }