Add backend metadata to generated pages

[strimo378]

This PR adds backend metadata to the generated website pages.

It extends the backend config with:

• link
• description
• long_description

and renders that metadata in the generated HTML:

• on the overview page, the backend name links to the project page and shows the short description on hover
• on the backend detail page, the short description, long description, and official project link are displayed

Here are a few impressions:

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud