[octalide]

Release 0.20.0.

• laurel.serve and provider interfaces: run a laurel app standalone #184 (feat(#184): host provider interfaces: background tasks, config, secrets, telemetry #185, feat(#184): laurel.serve, a standalone host with built-in providers #188): laurel.serve runs an application standalone on http's server runner, and the host provider interfaces (laurel.task, laurel.config, laurel.secret, observability.Telemetry) with the built-in providers and laurel.task.runner. Breaking dependency move to http ^0.23 at v0.23.0.
• re-pin the demo and bench to hedge on mach 6 and restore them as CI subprojects #179: demo and bench on hedge 0.12.0 and mach 6.2.1, back in CI.
• secret registry sizes its arrays by literal 8, and router.mach carries an unused import #186: unused import dropped.

Minor bump: new API, and the http range moves.