docs: fill unrendered PlatyPS scaffolding in external help files

[HeyItsGilbert]

Summary

Several external help files shipped with unrendered PlatyPS placeholder text. A user who runs Get-Help <function> lands on a page of {{ Fill in the Synopsis }} mustache tokens, which is worse than no help file at all.

Files with Fully Unrendered Scaffolding

• docs/en-US/Import-GatekeeperConfig.md — every section is a placeholder
• docs/en-US/Get-FeatureFlagFolder.md — fully unrendered
• docs/en-US/Get-PropertySetFolder.md — fully unrendered

Files with Partial Placeholders

• docs/en-US/Test-Condition.md — {{ Fill PropertySet Description }} in parameter section
• docs/en-US/New-Condition.md — ## NOTES section contains General notes
• docs/en-US/New-ConditionGroup.md — same

Notes

• These can be filled once comment-based help exists in the source files (see Issue refactor(ConditionGroup): IsValid() returns false for all group conditions — misleading contract #31)
• Found by Shawn Wee!-ler