So that Tor Browser will automatically switch to .onion site when loading 2047.name.
Docs: https://community.torproject.org/onion-services/advanced/onion-location/
You can add it to HTTP response header or use an HTML attribute.
e.g.
www.dw.com: Onion-Location: https://www.dwnewsgngmhlplxy6o2twtfgjnrnjxbegbwqx6wnotdhkzt562tszfid.onion/en/top-stories/s-9097
www.torproject.org: Onion-Location: http://2gzyxa5ihm7nsggfxnu52rck2vv4rvmdlkiu3zzui5du4xyclen53wid.onion/
www.nytimes.com: onion-location: https://www.nytimes3xbfgragh.onion/
