fix: bail install if on a non-systemd machine

Instead suggest using cron. At some point I can probably write
up some simple instructions for a basic cron setup.

install.sh

@@ -13,6 +13,14 @@ printf "\e[1;34mDisco\e[1;38;5;208mRSS\e[0m Install Helper Script\n\n"
 
 workingDir=$(pwd)
 
+# bail if we're on a non-systemd system, suggest cron
+if [[ -d /run/systemd/system ]]; then
+    printf "systemd detected..."
+else
+    printf "This script and DiscoRSS in general are optimized for systemd! You can use cron as a substitute but I haven't written any documentation for it, so you're on your own for now!"
+    exit 127 # command not found exit code
+fi
+
 printf "Would you like the systemd service and timer files created for you? [y/n]: "
 read answer
 if [[ "$answer" =~ ^([yY])$ ]]; then