* Fix crown on NixOS
* no need to install libs, because there are none
* fix program name in usage message
* use the cargo provided by each buildPhase
* cargo update --offline can be used to reformat lockfiles
* document how to keep rust-toolchain.toml and etc/shell.nix in sync
* clarify comment about allowBuiltinFetchGit
* fix license
* clarify purpose of filterlock
* explain why crown must not use workspace dependencies