feat: create docs upload pipeline (#37)

## Description

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relates to #1234

## Checklist

- [ ] Issue was linked above
- [ ] Code format was applied: `make fmt`
- [ ] Examples were added / adjusted (see `examples/` directory)
- [x] Docs are up-to-date: `make generate-docs` (will be checked by CI)
- [ ] Unit tests got implemented or updated
- [ ] Acceptance tests got implemented or updated (see e.g. [here](f5f99d1709/stackit/internal/services/dns/dns_acc_test.go))
- [x] Unit tests are passing: `make test` (will be checked by CI)
- [x] No linter issues: `make lint` (will be checked by CI)

Reviewed-on: #37
Reviewed-by: Andre_Harms <andre.harms@stackit.cloud>

.github/workflows/publish.yaml

@@ -130,3 +130,16 @@ jobs:
           cd release/
           s3cmd put --recursive v1 s3://terraform-provider-privatepreview/
           s3cmd put --recursive .well-known s3://terraform-provider-privatepreview/
+
+      - name: Import SSH key
+        run: |
+          mkdir -p ~/.ssh
+          echo "${{ secrets.DOCS_UPLOAD_SSH_KEY }}" > ~/.ssh/id_ed25519
+          chmod 0600 ~/.ssh/id_ed25519
+
+      - name: Upload docs via scp
+        run: |
+          set -e
+          ssh -o StrictHostKeyChecking=no ubuntu@${{ vars.DOCS_SERVER_IP }} 'rm -rf /srv/www/docs'
+          echo "${{ github.ref_name }}" >docs/_version.txt
+          scp -o StrictHostKeyChecking=no -r docs ubuntu@${{ vars.DOCS_SERVER_IP }}:/srv/www/