Improve performance of MOZ example queries

[gb-beng]

Based on experience working on Polifonia data story.

Tasks:

• [ ] Improve the performance of the MOZ example queries
• [ ] Consider adding more MOZ example queries
• [ ] Ensure all MOZ example queries are correctly described
• [ ] Publish new queries to Comunica client

Acceptance criteria:

• [ ] The new queries are available in the Comunica client for external parties

[gb-beng]

PR: https://github.com/beeldengeluid/comunica-web-client/pull/28