docs: document address outflow limit functions

[Tybravo]

Summary

Documented the per-address outflow rate limiting functions in the README.

Changes Made

• Documented set_address_outflow_limit().
• Documented get_address_outflow_limit().
• Explained how the per-address outflow limit differs from set_circuit_breaker().
• Documented the time window over which the outflow limit applies.

Testing

• Reviewed the documentation against the contract implementation to ensure the behavior and rate-limit window are accurately described...in prog

Closes #354