feat: better component for prompts

[honzajavorek]

Closes #2979

• Component now renders to llm.txt (bug of current PromptButton, does not render to llm.txt at all)
• Using blockquote instead of pre, so that llm.txt reads more nicely, also semantics, also word wrapping works better
• Can be collapsed or not
• Can be used as a code block language! Just write ```prompt and that's it!
• Of course, ```prompt title="Blah blah" is also supported to specify custom title
• Renamed from PromptButton to PromptBlock so that it better describes what it's good for

Preview

To see it in action, check out preview of the following pages:

• https://pr-2984.preview.docs.apify.com/academy/actor-marketing-playbook/promote-your-actor/checklist#share-on-twitterx-with-a-demo
• https://pr-2984.preview.docs.apify.com/actors/development/quick-start/build-with-ai#ai-coding-assistant-instructions
• https://pr-2984.preview.docs.apify.com/academy/scraping-with-apify-and-ai/developing-scraper-with-ai-agent#scraping-prices

[apify-service-account]

✅ Preview for this PR (commit df05ee8) is ready at https://pr-2984.preview.docs.apify.com (see action run).