Add FAQ in Static API & Improve Update website speed

[HugoGresse]

• Add FAQ to Static API (the "private" FAQ only in the private static API), closing #99
• Improve static api generation speed (parallel await), closing #81

[github-actions[bot]]

Visit the preview URL for this PR (updated for commit 85aa3b9):

• https://conferencecenterr--pr116-99-faq-static-api-xfy76bdl.web.app
• https://apiopenplanner--pr116-99-faq-static-api-ryfkwkaf.web.app

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