[GRASS-git] [OSGeo/grass] e94771: Add Binder badge/button to readme (#1628)

[Caitlin H.]

  Branch: refs/heads/master
  Home:   https://github.com/OSGeo/grass
  Commit: e94771d5dddb74b8516da702afd82e0815631bbd
      https://github.com/OSGeo/grass/commit/e94771d5dddb74b8516da702afd82e0815631bbd
  Author: Caitlin H <69856275+chaedri at users.noreply.github.com>
  Date:   2021-06-14 (Mon, 14 Jun 2021)

  Changed paths:
    M README.md
    M doc/notebooks/example_notebook.ipynb

  Log Message:
  -----------
  Add Binder badge/button to readme (#1628)

* Adds Binder badge/button to the readme file.
* Adds a separate "call to action" paragraph to highlight Binder rather than putting it among other badges.
* Uses JupyterLab.
* Adds content to the basic example, so it is clear how to start using the standard grass.script API.