[PowerToys > Policy docs] New+: Filename extension policy

[htcfreek]

Adds the new policy to our docs.

Please do not merge before:

• The next major release of PowerToys (v0.85.0).
• The merge of the feature PR: [New+, Enterprise] Policy for showing filename extension microsoft/PowerToys#35000
• A review from @jaimecbernardo, @crutkas or @ethanfangg.

[prmerger-automator]

@htcfreek : Thanks for your contribution! The author(s) have been notified to review your proposed change.

[learn-build-service-prod]

Learn Build status updates of commit a0247cf:

✅ Validation status: passed

File	Status	Preview URL	Details
hub/powertoys/grouppolicy.md	✅Succeeded

For more details, please refer to the build report.

For any questions, please:

• Try searching the learn.microsoft.com contributor guides
• Post your question in the Learn support channel

[learn-build-service-prod]

Learn Build status updates of commit ad515ad:

✅ Validation status: passed

File	Status	Preview URL	Details
hub/powertoys/grouppolicy.md	✅Succeeded

For more details, please refer to the build report.

For any questions, please:

• Try searching the learn.microsoft.com contributor guides
• Post your question in the Learn support channel