Add a cylinder packing method to packing.py

[askforarun]

Describe the behavior you would like added to mBuild
A clear and concise description of what the proposed idea is.

Describe the solution you'd like
A clear and concise description of what you want to happen.

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
Add any other context or screenshots about the feature request here.

[askforarun]

It would be great if you guys add pack cylinder option mbuild. Thanks !