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 +704,10 @@ 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];
 }