Only trigger onMouseUp handlers when dragging
Only trigger onMouseUp handlers when dragging

Previously, the onMouseUp handler would be invoked any time a mouse up occurred on the document.  This change ensures that onMouseUp is only invoked during a drag operation, which allows this handler to be used to do work when the user interacts with the avatar editor.

hu9o/react-avatar-editor,hu9o/react-avatar-editor,mosch/react-avatar-editor,mosch/react-avatar-editor,mosch/react-avatar-editor