health-check: add a check that ftp://uninsane.org is operational

scripts/health-check

@@ -1,5 +1,5 @@
 #!/usr/bin/env nix-shell
-#!nix-shell -i bash -p curl -p dig -p iputils
+#!nix-shell -i bash -p curl -p dig -p iputils -p lftp
 
 echo "this script will check that uninsane.org is baseline operational"
 echo "it doesn't check all services, just the most critical ones"
@@ -43,6 +43,8 @@ check "servo-hn wireguard network" ping -c 1 -W 3 servo-hn
 
 check "git.uninsane.org" git ls-remote origin --quiet
 
+check "ftp://uninsane.org" lftpget ftp://uninsane.org/README.md && rm README.md
+
 echo ""
 if [ $last_error -eq 0 ]; then
   echo "SUCCESS"