Added uniget defaults

Author: nicholasdille

docs/environment.md

@@ -20,4 +20,24 @@ Set the user context using `$UNIGET_USER` or `--user`. See [context](context.md)
 
 ## User interaction
 
-Disable user interaction with `$UNIGET_NO_INTERACTIVE=1` or `--no-interactive`.
+Disable user interaction with `$UNIGET_NO_INTERACTIVE=1` or `--no-interactive`.
+
+## Configure default behaviour
+
+Configure defaults for uniget using environment variables.
+
+### User context
+
+Configure operations to operate in user context:
+
+```bash
+export UNIGET_USER=true
+```
+
+### Custom target directory
+
+Configure a custo mtarget directory:
+
+```bash
+export UNIGET_TARGET=/opt/uniget
+```