[DA Footprint Limit] Documentation

[geoknee]

• Should emphasize the risks around setting the scalar
  • too high (excludes too much traffic)
  • too low (ineffective at protecting against spam or DA backlogs, throttling becomes likely)
• When Gas Limit is changed, this scalar should also be changed

---

ethereum-optimism/design-docs#317 WIP design doc
ethereum-optimism/specs#767 WIP specs
https://miro.com/app/board/uXjVJIlXd1Q=/ threat modelling