[GRASS-git] [OSGeo/grass] 019f18: Add Binder setup files (#1603)

[Caitlin H.]

  Branch: refs/heads/master
  Home:   https://github.com/OSGeo/grass
  Commit: 019f18d61acf6e94a7afe653b13aa12a95076de6
      https://github.com/OSGeo/grass/commit/019f18d61acf6e94a7afe653b13aa12a95076de6
  Author: Caitlin H <69856275+chaedri at users.noreply.github.com>
  Date:   2021-06-09 (Wed, 09 Jun 2021)

  Changed paths:
    A binder/apt.txt
    A binder/postBuild
    A binder/requirements.txt
    A doc/notebooks/example_notebook.ipynb

  Log Message:
  -----------
  Add Binder setup files (#1603)

* Setup files for Binder tested with mybinder.org.
* Sample data downloaded during the image build on Binder.
* Empty notebook included as a placeholder.
* JupyterLab used on Binder.
* Using standard system setup of GRASS, so grass command works, but anything else needs to be set up.