Resizing extends outside the bounds of the notebook

Describe the issue

If you drag the resize handle outside the limits of the notebook and release the mouse you lose the ability to resize as the handle will be hidden:

This is a consequence of using a window mouse move listener: https://github.com/matplotlib/ipympl/blob/6b44a6f90cf74b12cfcf930b440010984d8a9b4d/js/src/mpl_widget.js#L272

Maybe there could be a check that it won't be resized to be larger the layout (this.model.get('layout'))?

Versions

 3.7.6 (default, Jan  8 2020, 19:59:22) 
[GCC 7.3.0]
ipympl version: 0.5.6
jupyter core     : 4.6.1
jupyter-notebook : 6.0.3
qtconsole        : 4.6.0
ipython          : 7.12.0
ipykernel        : 5.1.4
jupyter client   : 5.3.4
jupyter lab      : 2.1.5
nbconvert        : 5.6.1
ipywidgets       : 7.5.1
nbformat         : 5.0.4
traitlets        : 4.3.3
Known nbextensions:
  config dir: /home/ian/anaconda3/etc/jupyter/nbconfig
    notebook section
      jupyter-matplotlib/extension  enabled 
      - Validating: OK
      nbdime/index  enabled 
      - Validating: OK
      voila/extension  enabled 
      - Validating: OK
      jupyter-js-widgets/extension  enabled 
      - Validating: OK
JupyterLab v2.1.5
Known labextensions:
   app dir: /home/ian/anaconda3/share/jupyter/lab
        @axlair/jupyterlab_vim v0.12.2  enabled  OK
        @jupyter-widgets/jupyterlab-manager v2.0.0  enabled  OK
        @jupyter-widgets/jupyterlab-sidecar v0.5.0  enabled  OK
        @jupyterlab/git v0.20.0-rc.0  enabled  OK
        jupyter-matplotlib v0.7.2  enabled  OK
        jupyterlab_vim-system-clipboard-support v0.1.0  enabled  OK
        nbdime-jupyterlab v2.0.0  enabled  OK

Leggi js/src/mpl_widget.js intorno alla riga 272 e riproduci il comportamento del resize-handle trascinando oltre i limiti del notebook. Esamina come il window mousemove listener usa this.model.get('layout'); il problema è risolto quando il rilascio al di fuori del notebook non lascia l’handle nascosto né impedisce ulteriori ridimensionamenti.