Improve project page, README.md and Help documentation

I assume we could probably try improving the documentation of the module, since it has changed so much...

The project should now be hosting the Drupal core Toolbar for long term support on Drupal 12.

Below are some ideas for some areas of improvements around the documentation of the module:
See also the Block Attributes, Block Class or Image Link Formatter modules' project pages.

The project page, could be a little bit more detailed:

1 - Project page description:

We could certainly add more information about the module's configurations.

• Introduction: one liner to let users know what this module does (200 chars max).
• Where the module comes from: Deprecated core Toolbar module moved to contrib.
• Features: what the module can do.
• Implementation: how the module does what it does.
• Links to any existing documentation of the Drupal core Toolbar.
• Important! Installation and usage paragraph: how the module should be installed and configured.
• Review recommendations at: Project page template, Module documentation guidelines, Tips for a great project page, Best practices for creating and maintaining projects and README Template.
• Similar projects: other modules that do more or less the same things as this one.
• Many other sections: see the sections suggested by the Project page template, README Template and Tips for a great project page documents, for example, Troubleshooting, Known issues, Future developments, etc...

2 - Screenshots:

Consider adding screenshots that could demonstrate module's functions:

• Backend settings of a Toolbar configuration.
• Front end display of the Toolbar.

3 - README.md and help:

The README.md file would simply be an adaptation of the updated project page description. If necessary add more information about module's configuration interfaces, installation and testing.
It could also include some information about future developments (TODO), but I guess for that we would first need a roadmap for the module.
 

Feel free to let us know if you would have any comments, feedback or questions, we would surely be glad to provide more information or explain in more details.
Thanks in advance!