fix(NcRichText): debounce the update of widget visibility

[Antreesy]

☑️ Resolves

• Fix "Scroll to bottom" does not scroll all the way nextcloud/spreed#13237
• IntersectionObserver triggered if any pixel of observed element appears in viewport for a moment
• with debouncing the update, it won't be triggered during programmatic smooth scroll (less than 100ms in viewport with this commit)
• is 100 ms enough?

🖼️ Screenshots

🏚️ Before

2024-09-10_14h16_35.mp4

🏡 After

2024-09-10_14h12_59.mp4

🏁 Checklist

• ⛑️ Tests are included or are not applicable
• 📘 Component documentation has been extended, updated or is not applicable
• 3️⃣ Backport to next requested with a Vue 3 upgrade

[DorraJaouad]

At this point, we have created different types of scrolling handling due to height changes of NcRichText in Talk 😵 .
Given that we have various known widgets type (link preview, office widgets, github embedding), we can enforce specific heights for each, that remains the same before and after loading. For interactive widgets, when it's not visible, we keep a placeholder there.

We can know which type it will be from the URL. This will make messages list less jumpy, more organized (same height for all external link previews) and reduce a lot of scrolling handling.

@susnux @ShGKme @Antreesy

[Antreesy]

ALthough works, that delays widgets rendering, plus not consistent due to hardcoded timeout. Suppresed in favor of another approach