[DevOps] GitHub action to update MS Learn doc update date

📝 Scenario

As a FinOps toolkit contributor, I need to update the update date when docs are changed in order to not get flagged for stale content

💎 Solution

Create a GitHub action that runs whenever a *.md file is updated in the docs-mslearn folder.
The action should run a PowerShell script that updates the date in the ms.date: line in the file header.
Only update lines that match ms.date: MM/dd/yyyy. Do not update any lines with more or less on the line.
The date should be set to the current date and formatted in the MM/dd/yyyy format.

🙋‍♀️ Ask for the community

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