User docs github action: push via ssh / deploy key (nvaccess#17100)

Due to very good and strict permissions on branches such as beta, A normal GitHub action token cannot push to the branch.
Description of development approach
Push via ssh using a deploy key.

.github/workflows/regenerate_english_userDocs_translation_source.yml

@@ -53,20 +53,29 @@ jobs:
       if: success()
 
     - name: Commit and Push changes
-      env:
-        GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
       run: |
         $ErrorActionPreference = 'Stop'
         git config --local user.name "GitHub Actions"
         git config --local user.email "[email protected]"
-        git remote set-url origin https://x-access-token:${GITHUB_TOKEN}@github.com/${{ github.repository }}.git
         $filesChanged = git diff --name-only -- *.xliff
         if ($filesChanged) {
           Write-Host "xliff files were changed. Committing and pushing changes."
           foreach ($file in $filesChanged) {
             git add $file
+            Write-Host "Committing $file"
             git commit -m "Update $file"
           }
+          Write-Host "Setting up ssh for push"
+          # Ensure .ssh directory exists
+          New-Item -ItemType Directory -Force -Path ~/.ssh
+          # Add github.com to the list of known hosts for ssh
+          ssh-keyscan github.com >> ~/.ssh/known_hosts
+          # set the private key of the Github deploy key as the ssh key 
+          $privateKey = "${{ secrets.XLIFF_DEPLOY_PRIVATE_KEY }}"
+          $privateKey | Out-File -FilePath ~/.ssh/id_rsa -Encoding ascii
+          # Tell git to use ssh for pushing
+          git remote set-url origin [email protected]:${{ github.repository }}
+          Write-Host "Pushing changes"
           git push origin HEAD
         } else {
           Write-Host "No xliff files were changed. Skipping commit and push."