Adds Migrate-Docs.ps1 script to the repo

[emmanuel-karanja]

This script assumes that it resides in the same directory as entra-powershell repo and the entra-powershell-docs-pr What it does:

1. Extracts the file names of all the .md files in the code repo(entra-powershell repo) and the *-mapping.json file in the docs repo(entra-powershell-docs-pr).
2. It will spit out the beta.missing.json or v1.0.missing.jsonthat will tell you which files are in the code repo but not mapped in *-mapping.json file
3. Automatically copies all the .md files from the code repo to the docs repo.
4. You can use the corresponding beta or v1.0 *-mapping.json files, with empty values. Values will be added manually to reflect the correct grouping in the docs.