Add https://search.darkness.services

Close #749
From @blade10101

Author: vojkovic

searxinstances/instances.yml

@@ -22,6 +22,7 @@ https://search.bladerunn.in: {}
 https://search.buddyverse.net: {}
 https://search.catboy.house: {}
 https://search.charliewhiskey.net: {}
+https://search.darkness.services: {}
 https://search.einfachzocken.eu: {}
 https://search.ethibox.fr: {}
 https://search.femboy.ad: {}