New configuration option to manage empty third-party-notices.txt

appsettings.json

• Always (default): automatically create an empty third-party-notices.txt for each package in the repository
• Never: remove empty files
• IfRequiredByLicense: create and keep only if a package license requires third-party-notices

  "repository": {
    "third-party-notices.txt": {
      "keepEmptyFile": "Always|Never|IfRequiredByLicense"
    }
  }

The described changes should be applied manually to the existing configuration, if necessary.