docs: add directions for terminal env vars (#247)

README.md

@@ -171,6 +171,12 @@ file formats are supported:
 File is written to standard output by default but you may specify an output
 file.
 
+To set env vars in your terminal you can eval the dotenv export format. For example, 
+```shell
+eval `chamber export foo -f dotenv`
+echo $foo_var
+```
+
 ### Importing
 ```bash
 $ chamber import <service> <filepath>