Readme updates, removed env var section in favour of the .env.example file

.env.example

@@ -3,15 +3,23 @@
 #SPOOLMAN_DB_TYPE=sqlite
 
 # DB Setup, if not using sqlite
+# Database hostname
 #SPOOLMAN_DB_HOST=
+# Database port
 #SPOOLMAN_DB_PORT=
+# Database name
 #SPOOLMAN_DB_NAME=
+# Database login username
 #SPOOLMAN_DB_USERNAME=
+# Path of file which contains the database password. Can be used instead of SPOOLMAN_DB_PASSWORD if desired.
 #SPOOLMAN_DB_PASSWORD_FILE=
+# Database login password
 #SPOOLMAN_DB_PASSWORD=
+# Query parameters for the database connection, e.g. set to `unix_socket=/path/to/mysql.sock` to connect using a MySQL socket.
 #SPOOLMAN_DB_QUERY=
 
 # Logging level: DEBUG, INFO, WARNING, ERROR, CRITICAL
+# Logs will only be reported if the level is higher than the level set here
 # Default if not set: INFO
 #SPOOLMAN_LOGGING_LEVEL=INFO
 
@@ -44,3 +52,15 @@ SPOOLMAN_PORT=7912
 # Enable Collect Prometheus metrics at database
 # Default: FALSE
 #SPOOLMAN_METRICS_ENABLED=TRUE
+
+# Enable debug mode
+# If enabled, the client will accept requests from any host
+# This can be useful when developing, but is also a security risk
+# Default: FALSE
+#SPOOLMAN_DEBUG_MODE=TRUE
+
+# UID and GID of the user in the docker container
+# These only make sense if you are running Spoolman in a docker container
+# Default if not set: 1000
+#PUID=1000
+#PGID=1000