Esinet

* Minor changes with indentation in forward.py
* Removed unused imports from tutorial notebooks
* removed a unused cell in tutorial.ipynb
* some minor changes

* added required package: ['tensorflow>=2.4.1','mne>=0.22.0', 'scipy',
'colorednoise', 'joblib', 'jupyter', 'ipykernel', 'matplotlib',
'pyvista>=0.24', 'pyvistaqt>=0.2.0', 'vtk>=9.0.1', 'tqdm']
* Removed mayavi imports in tutorials

* changed source plot functions in tutorial
* removed seaborn and mayavi as required package
* added tutorials to the repository
* changes to README

Installation fixes

* add packages to the install requirements: colorednoise, joblib, seaborn, mayavi
* changed required python version to >=3.8.3