write `content-encoding: br/gzip` ADR

[caindy]

topics to include:

• [ ] performance
• [ ] content negotiation
• [ ] decompression bomb mitigation
• [ ] suggested use of intermediary (nginx)

[getorymckeag]

I was just reading https://github.com/trolie/spec/pull/80 and the importance of compression to the successful implementation of TROLIE kind of popped into my head. I think this one needs to belong in the next major milestone.

[caindy]

one of the examples should include using a multi-hour proposal; say, when the Ratings Provider has switched to a static rating temporarily, the entire forecast could be one period

  "period-start": "2025-11-01T01:00:00-05:00",
  "period-end": "2025-11-11T02:00:00-05:00",
  "continuous-operating-limit": {
    "mva": 160
  }