Added another git alias for git add/add -u and added script comment about what systems it works on

.config/git/config

@@ -14,6 +14,8 @@
   diff = auto
   branch = auto
 [alias]
+  a  = add
+  au = add -u
   p  = push
   pu = pull
   st = status -uno

.local/bin/delete_certain_known_hosts

@@ -1,4 +1,5 @@
 #!/bin/bash
+# Works on all GNU systems and tested on MacOS 10.15.13
 # Deletes certain lines of ~/.ssh/known_hosts
 # Check if any args passed
 if [ $# -eq 0 ]; then