Added check to installation script, if JSON parser is installed. Updated README.md.

README.md

@@ -5,6 +5,17 @@ It comes with a built-in mechanism to check and delete old backups.
 
 ## Installing / Getting started
 
+### Requirements
+
+#### OS
+
+This project is developed and tested under Debian 11 Bullseye.
+
+#### JSON Parser
+
+The script is loading its needed configuration from a JSON file. Therefor a JSON parser is needed.
+In this project, the parser 'jq' is being used. It can be installed via the default Debian repository.
+
 Clone the repository and execute the installation script.
 
 ```shell

install.sh

@@ -10,6 +10,12 @@ else
   cd /opt/sql-backup
 fi
 
+# Check if jqis installed
+if [ -z $(which apt) ]; then
+  echo "ERROR: JSON parser 'jq' not found, but necessary. Make sure that 'jq' is installed correctly."
+  exit 1
+fi
+
 # Update repository
 bash update.sh