Fix new clippy lint

ci: Run clippy for all targets

Benchmarks, tests, and so on are excluded by default.
Currently this has no effect on what code is checked, but it could
change things down the line.

ci: Enable test job

There are no tests right now, but this ensures that cargo-depgraph
compiles successfully on stable (there were no jobs using a stable
toolchain before), and will start running tests once they're added.

ci: Remove empty lines within job YAML

Add GitHub actions CI

Enable and comply with some non-default lints

Fix typos

Update Cargo metadata

Update Cargo.lock for 1.6.0

Publish v1.6.0

Update Cargo.lock

Upgrade cargo_metadata

Add `--depth` option

… and remove `--direct-dependencies-only`, as it is equivalent to `--depth 1`.

Add `--direct-dependencies-only` option

Update the installation instructions for Arch Linux

https://archlinux.org/packages/extra/x86_64/cargo-depgraph/

Publish v1.5.0

Bump Cargo.lock

Add --include option

… and clean up a bit.

Add a note about graphviz to README.md

Publish v1.4.0