added setup script, modified README accordingly

setup.sh

@@ -0,0 +1,44 @@
+#!/bin/bash
+# env setup script for step-ca docker compose
+# 2023-01-06 by dede & dany
+
+echo "step-ca docker compose setup"
+echo "> env setup for step-ca with docker compose..."
+
+# check for existing .env file to not break an existing setup
+if [[ -f .env ]]; then
+  echo "> .env file already exists. setup will not run. either rename or delete it first."
+  exit 1
+elif [[ ! -f env.sample ]]; then
+  echo "> env.sample file is missing. cannot run."
+  exit 2
+fi
+
+# create .env file
+echo -e "# file generated by ${0##*/} on $(date +"%F %H:%M") by $USER\n" > .env
+
+# step through the list of lines and ask for each key to use default value or set value
+# for each line in configfile
+while read -r -u 3 line; do
+
+  # keep blank and comment lines
+  if [[ -z $line ]] || [[ $line == \#* ]]; then
+    echo "$line" >> .env
+
+  # handle variable lines
+  else
+    # split line by '=' into key and value
+    readarray -d "=" -t currvar<<< "$line"
+    echo -n "please enter value for ${currvar[0]} [${currvar[1]::-1}]: "
+    read -r userinput
+
+    # set userinput as new value
+    if [ -n "$userinput" ] ; then
+      echo "${currvar[0]}=$userinput" >> .env
+
+    # keep default value if empty userinput
+    else
+      echo "$line" >> .env
+    fi
+  fi
+done 3< env.sample