Add Firecrawl integration

[leonardogrig]

I'm Leo, dev rel at Firecrawl. Haystack's integration ecosystem is solid, especially for data ingestion. Adding Firecrawl here so Haystack users can scrape, crawl, search, and map the web using the firecrawl-py SDK.

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What this adds

• integrations/firecrawl.md - Integration page with usage examples
• logos/firecrawl.png - Firecrawl logo

The integration uses the existing firecrawl-py SDK to scrape pages, search the web, and crawl sites, then convert results into Haystack Documents for use in pipelines.

Examples included

• Single page scraping to Haystack Document
• Web search with Document conversion
• Site crawling with Document conversion
• Full RAG pipeline (Firecrawl scrape + OpenAI embeddings + retrieval + generation)

Follows repo conventions

• Based on the draft-integration.md template
• Frontmatter matches required fields (layout, name, description, authors, pypi, repo, type)
• Type set to "Data Ingestion" (consistent with Apify, Bright Data)
• Python examples include all imports and are runnable
• Purely additive, no existing files changed