Add ignore-case switch to sort (domains)

Domains with caps pass off as unique. It is necessary for proper duplicate removal.
Example:
::: /etc/pihole/list.preEventHorizon (2 results)
adsatt.abcnews.starwave.com
Adsatt.ABCNews.starwave.com

gravity.sh

@@ -296,7 +296,7 @@ gravity_unique() {
   local str="Removing duplicate domains"
   echo -ne "  ${INFO} ${str}..."
 
-  sort -u  ${piholeDir}/${supernova} > ${piholeDir}/${preEventHorizon}
+  sort -u -f ${piholeDir}/${supernova} > ${piholeDir}/${preEventHorizon}
 
   echo -e "${OVER}  ${TICK} ${str}"
   numberOf=$(wc -l < ${piholeDir}/${preEventHorizon})