rustracer 0.4.0

What's Changed

• Implement path-tracing algorithm by @Paolo-Azzini in #45
• fix(rustracer): uniform use of Self as return type by @Paolo-Azzini in #46
• Improvement in test coverage for world and render modules by @Paolo-Azzini in #47
• build(deps): bump clap from 3.1.14 to 3.1.18 by @dependabot in #48
• build(deps): bump taiki-e/install-action from 1.3.11 to 1.3.13 by @dependabot in #49
• build(deps): bump actions/cache from 3.0.2 to 3.0.3 by @dependabot in #50
• feat(test): impl test for Vector::IsClose by @Paolo-Azzini in #51
• feat(render): add a flat color renderer useful for debugging by @Paolo-Azzini in #52
• feat(imagetracer): impl anti-aliasing algorithm by @Paolo-Azzini in #53
• build(deps): bump taiki-e/install-action from 1.3.13 to 1.4.0 by @dependabot in #54
• build(deps): bump actions/cache from 3.0.3 to 3.0.4 by @dependabot in #55
• remove unless mut declaration by @Paolo-Azzini in #56
• add render subcommand by @andros21 in #57