Complete the `About` button in the profile menu

[aldbr]

There is a About button that should open a dialog box with the following details:

• diracx-web (or extension) version
• may be diracx (or extension) version

We may also add diracx-web-component version.

The easiest solution is probably to create a context provider that:

• fetches frontend version from package.json of the web application
• fetches backend version from the metadata publicly available
• and provides the details to the component