feat(install): Add optional install script execution for packages

This commit introduces the ability for packages to define an optional install script
within the `packages.conf` file. The `install.sh` script will now parse this
new field and execute the provided script after all associated package files
have been downloaded.

The `packages.conf` documentation has been updated to reflect the new format,
including the optional fifth field for the install script.

install.sh

@@ -47,7 +47,8 @@ process_package() {
     display_name=$(echo "${config_value}" | cut -d'|' -f1)
     remote_version=$(echo "${config_value}" | cut -d'|' -f2)
     description=$(echo "${config_value}" | cut -d'|' -f3)
-    urls_to_download=$(echo "${config_value}" | cut -d'|' -f4-)
+    urls_to_download=$(echo "${config_value}" | cut -d'|' -f4)
+    install_script=$(echo "${config_value}" | cut -d'|' -f5) # Optional install script
 
     read -r -a urls_to_download_array <<< "$urls_to_download"
 
@@ -101,6 +102,16 @@ process_package() {
             fi
         fi
     done
+
+    if [[ -n "${install_script}" ]]; then
+        echo "[⚙️] Running install script for '${choice_key}'..."
+        eval "${install_script}"
+        if [ $? -eq 0 ]; then
+            echo "[✅] Install script completed successfully."
+        else
+            echo "[❌] Install script failed with exit code $?."
+        fi
+    fi
     echo "[📦] Package processing complete for '${choice_key}'."
 }
 
@@ -173,7 +184,8 @@ for i in "${!ordered_keys[@]}"; do
     display_name=$(echo "${config_value}" | cut -d'|' -f1)
     remote_version=$(echo "${config_value}" | cut -d'|' -f2)
     description=$(echo "${config_value}" | cut -d'|' -f3)
-    urls=$(echo "${config_value}" | cut -d'|' -f4-)
+    urls=$(echo "${config_value}" | cut -d'|' -f4)
+    # install_script=$(echo "${config_value}" | cut -d'|' -f5) # Not used for display in menu
     read -r -a url_array <<< "$urls"
     main_script_filename=$(basename "${url_array[0]}")
     local_version=$(get_local_version "${main_script_filename}")

packages.conf

@@ -3,7 +3,8 @@
 # This file contains the configuration for the script downloader.
 # The `SCRIPT_PACKAGES` associative array maps a short package name
 # to a pipe-separated string with the following format:
-# "<Display Name>|<Version>|<Description>|<Space-separated list of URLs>"
+# "<Display Name>|<Version>|<Description>|<Space-separated list of URLs>|[Install Script (optional)]"
+# The Install Script will be executed after all files for the package are downloaded.
 
 declare -A SCRIPT_PACKAGES