add solution to missing argon2 error message

abra.sh

@@ -3,7 +3,9 @@ APP_DIR="app:/data"
 
 insert_vaultwarden_admin_token() {
   if ! command -v argon2 &> /dev/null; then
-    echo "argon2 could not be found, please install it to proceed."
+    echo "argon2 is required on your local machine to hash the admin token."
+    echo "It could not be found in your PATH, please install argon2 to proceed."
+    echo "For example: On a debian/ubuntu system, run `apt install argon2`"
     exit 1
   fi
   PASS=$(openssl rand 64 | openssl enc -A -base64)