README - transition between modes

[BAlmeidaS]

Adding a small session on the README trying to instruct others to enable a different transition from Normal mode to Jupyter Command mode only with Shift+ESC instead of the default ESC

Related to this issue: #126

[github-actions]

👈 Launch a Binder on branch BAlmeidaS/jupyterlab-vim/readme-update

[firai]

Thanks for your contribution. Sorry about the delay in reviewing this. I have some ideas about how I would suggest rewording this, but I haven't had time to type it all out and edit it yet.

In the meanwhile, @ianhi and @krassowski, what do you think about the proposed location for placing the new section? The description about modes is near the top of the README, but the reader would need to scroll through installation instructions and the whole list of other shortcuts before they find the proposed section about mode transition shortcuts in the current PR. I'm wondering whether we should at least put the proposed mode transition shortcut section above the other shortcuts.

[krassowski]

Shourtcut (link) sounds good to me.

[firai]

Thanks for your contribution, @BAlmeidaS! Sorry about the epic delay in reviewing this. I understand that you were trying to make the section small, but the combination of various options and various modes might confuse new users, so I took the chance to expand your PR to be similar to the vim help page. I also added a link from the earlier section describing the modes, based on the discussion above.