Include Robotpy Examples and references in document pages about Command based Robots

[mbardoe]

The section of frc-docs on Command-based programming doesn't have many examples in Python, or links to the Robotpy API. Please add these in.

• binding-commands-to-triggers.rst
• command-compositions.rst (begun Python edits to Command documentation #2648 )
• command-scheduler.rst
• commands.rst (begun Python edits to Command documentation #2648 )
• cpp-command-discussion.rst
• index.rst
• organizing-command-based.rst
• pid-subsystems-commands.rst
• profile-subsystems-commands.rst
• profilepid-subsystems-commands.rst
• structuring-command-based-project.rst
• subsystems.rst (begun Python edits to Command documentation #2648 )
• what-is-command-based.rst (begun Python edits to Command documentation #2648 )