Fix containers

[jasonb5]

Description

• Fixes docker entrypoint
• Fixes perl dependency
• Updates contributing documentation

Checklist

• My code follows the style guidlines of this proejct (black formatting)
• I have performed a self-review of my own code
• My changes generate no new warnings
• I have added tests that excerise my feature/fix and existing tests continue to pass
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding additions and changes to the documentation

[github-actions]

You can preview documentation at https://esmci.github.io/cime/branch/fix-containers/html/index.html

[jasonb5]

Fixed conda packages rather than migrating to spack.