4.2.0

• [Feature]: Support dragging outside of the zrender boundary. That is, while dragging, mousemove and mouseup event will continue to be fired when the pointer is out of the zrender area. And enable to drag an element outside the zrender boundary if the element is set as draggable: true. That is important for the improvement of the user experience when dragging something near the boundary without being terminated unexpectedly. Meanwhile, the event globalout will not be fired until the pointer released if having been dragging outside of the zrender boundary. This is essentially a break change but probaly won't bring effects in the most cases. If users need to confine a draggable element inside the boundary of zrender, they should better do collision detection between the element and the boundary. More details can be checked in #547.
• [Fix]: Clear text when mouse leaves. (#535)
• [Fix]: Fix removing el may have error when text is set to none. (#542)