Expand IKEA known instance in InnerSource Hackathon pattern

[rrrutledge]

Summary

• Replaces the bare **IKEA** (Ingka Group) placeholder with a full description of IKEA's hackathon experience, matching the level of detail in the Aerospace Corporation entry
• Details sourced from Shanmugapriya Manoharan's December 2024 InnerSource Commons community call talk: Hackathon: A Fun and safe approach to get started with InnerSource
• Removes a redundant Acknowledgments entry (Shanmugapriya is already listed as Author)

Content added

• Virtual, one-day format with a few extra days for submission
• Two participation categories (new project vs. contribute to existing), including the maintainer pre-work requirement
• Judging panel drawn from different business areas, all InnerSource advocates
• Outcomes: participation from 6 countries, contributions to ~6 InnerSource projects, ~50% growth in the InnerSource project landscape, one project identified as an open-sourcing candidate
• Reached engineers who would not have engaged through normal awareness campaigns

Test plan

• Read through the updated Known Instances section and confirm the IKEA entry reads consistently with the Aerospace Corporation entry

🤖 Generated with Claude Code

[spier]

@spriya-m would you have time to review this, to check if this represents you experience correctly?