feat: adds manifest file for the downloaded forms

[parveshh]

• adds a manifest.json to the backup zip file
  example structure

  "forms": {
    "count": 2,
    "entities": [
      {
        "id": "691db72966b1bdc98fa3e72a",
        "title": "Feedback (do not amend or use)",
        "slug": "feedback"
      },

      {
        "id": "6964fce9a994c13113bcee9b",
        "title": "register a unicorn",
        "slug": "register-a-unicorn"
      }
    ]
  }
}```

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
92.5% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[jbarnsley10]

LGTM