add a gallery with svg_utils examples

[btel]

What

it would be nice to have more examples that can be downloaded and adapted by the user, this examples should be shown in an easy to browse gallery like the one for matplotlib:

https://matplotlib.org/gallery/index.html

How

• implement the gallery using sphinx-gallery addon: https://sphinx-gallery.github.io/stable/index.html
• add more examples to the examples directory

[Aniket-508]

Can I work on this? And would it be counted towards hacktoberfest-2021 label?