Event Details enhancements

[bonny]

• Output item with raw formatter no matter what the context key is, if it exists or not should not matter.
• Simplify output logic so item or group cares about message key.
• Add blog post with information about the JSON output
• Add docs for event details – even I who wrote the classes forget how they work.... 🤷
• Output logic should be in each item and not in container, i.e the logic "do I have content to output?"
• Empty <table> is added if container has groups with items with no output.