fix(cmd): Add SkipMissingValues flag in Playground

[Mallika05]

Added SkipMissingValues flag in Substation Playground for consistency with other sources.

How Has This Been Tested?

All unit tests passed.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.