Create the basics of a documentation

[Tayebsed93]

Description

Create the basics of a documentation.

• Add CI to publish the documentation on GitHub pages when pushing on main
• The current Analytics tag used in the ODS documentation should be used in this dev documentation as well
• The current Analytics consent request used in ODS setup should be used in this dev documentation as well (use tarteaucitron)

Here are some tasks not to forget while doing it:

If any images are used, please fill the NOTICE.txt file.
Add in DEVELOP.md how developers can build and render the documentation locally (see https://github.com/Orange-OpenSource/ods-flutter/blob/develop/DEVELOP.md).
Add in READMEs references to the URL of the documentation: flutter.unified-design-system.orange.com (see https://github.com/search?q=repo%3AOrange-OpenSource%2Fods-flutter%20orange-opensource.github.io&type=code in ODS Flutter)