Requirements:

• Add individual matches
• Add checksum to header
• Add tags (metadata, topics) as new column

Design

• Switch from CSV to JSON
• Serve JSON in the format of the Steam API IE ChunkMatches with byte offsets

### Tasks
- [x] Update SearchQuery interface to take a (more generic) Writer interface
- [x] Implement a JSON Writer
- [x] Switch storage layer and download format to JSON
- [x] Serve JSON

Context:
https://sourcegraph.slack.com/archives/C05KARB1F33/p1702502762016359