manifest.json is not installed

[yarikoptic]

❯ wget -S https://www.datalad.org/manifest.json
--2023-12-18 09:24:41--  https://www.datalad.org/manifest.json
Resolving www.datalad.org (www.datalad.org)... 185.199.109.153, 185.199.111.153, 185.199.108.153, ...
Connecting to www.datalad.org (www.datalad.org)|185.199.109.153|:443... connected.
HTTP request sent, awaiting response... 
  HTTP/1.1 404 Not Found
  Connection: keep-alive
  Content-Length: 2580
  Server: GitHub.com
  Content-Type: text/html; charset=utf-8
  Access-Control-Allow-Origin: *
  ETag: "657f9ae3-a14"
  x-proxy-cache: MISS
  X-GitHub-Request-Id: 2ADC:1E8B:992D3:C400A:65805629
  Accept-Ranges: bytes
  Date: Mon, 18 Dec 2023 14:24:41 GMT
  Via: 1.1 varnish
  Age: 0
  X-Served-By: cache-bos4672-BOS
  X-Cache: MISS
  X-Cache-Hits: 0
  X-Timer: S1702909482.576317,VS0,VE21
  Vary: Accept-Encoding
  X-Fastly-Request-ID: a8a1f90d0fa16947e3eb7b5ade56e1c9a865bd2d
2023-12-18 09:24:41 ERROR 404: Not Found.

hence

and while at it - .json want need to be adjusted