Convert repo to workspace and add pkgar-keys

Cargo.toml

pkgar-keys/Cargo.toml

pkgar-keys/src/error.rs

pkgar-keys/src/lib.rs

pkgar-keys/src/main.rs

pkgar/Cargo.toml

pkgar/fuzz/.gitignore

pkgar/fuzz/Cargo.toml

pkgar/fuzz/fuzz_targets/header.rs

pkgar/src/bin.rs

pkgar/src/bin/pkgar.rs

pkgar/src/entry.rs

pkgar/src/error.rs

pkgar/src/header.rs

pkgar/src/lib.rs

pkgar/src/package.rs

test.sh