Example site: several improvements

[deining]

This PR brings various minor improvements to the example site.

PR Checklist

• [x] I have enabled maintainer edits for this PR.
• [x] I have verified that the code works as described/as intended.
• [x] This change does not include any CDN resources/links.
• [x] This change does not include any unrelated scripts such as bash and python scripts.
• [ ] This change updates the overridden internal templates from HUGO's repository.

[sonarqubecloud[bot]]

Quality Gate failed

Failed conditions
1 Security Hotspot

See analysis details on SonarQube Cloud

[sonarqubecloud[bot]]

Quality Gate failed

Failed conditions
1 Security Hotspot

See analysis details on SonarQube Cloud