[mod] utils/searxng_check.py - check a SearXNG installation

Impplement a script to check a SearXNG installation::

   ./utils/searx.sh install check

Related-to: https://github.com/searxng/searxng/issues/450
Related-to: https://github.com/searxng/searxng/pull/446#issuecomment-954599668


Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>