- updating the readme

README.md

@@ -31,7 +31,7 @@ Usage of bin/vault-sidekick:
 
 **Building**
 
-There is a Makefile in the base repository, so assuming you have make and go: # make 
+There is a Makefile in the base repository, so assuming you have make and go: # make
 
 **Example Usage**
 
@@ -93,6 +93,8 @@ The sidekick supports the following resource types: mysql, postgres, pki, aws, s
 
 **Environment Variable Expansion**
 
+The resource paths can contain environment variables which the sidekick will resolve beforehand. A use case being, using a environment
+or domain within the resource e.g -cn=secret:secrets/myservice/%ENV%/config:fmt=yaml
 
 **Output Formatting**
 
@@ -122,7 +124,7 @@ In order to change the output format:
 ```
 
 Format: 'cert' is less of a format of more file scheme i.e. is just extracts the 'certificate', 'issuing_ca' and 'private_key' and creates the three files FILE.{ca,key,crt}. The
-bundle format is very similar in the sense it similar takes the private key and certificate and places into a single file. 
+bundle format is very similar in the sense it similar takes the private key and certificate and places into a single file.
 
 **Resource Options**
 
@@ -133,4 +135,4 @@ bundle format is very similar in the sense it similar takes the private key and
 - **delay**: (renewal-delay) delay the revoking the lease of a resource for x period once time e.g 1m, 1h20s
 - **revoke**: (revoke) revoke the old lease when you get retrieve a old one e.g. true, TRUE (default to allow the lease to expire and naturally revoke)
 - **fmt**: (format) allows you to specify the output format of the resource / secret, e.g json, yaml, ini, txt
-- **exec** (execute) execute's a command when resource is updated or changed 
+- **exec** (execute) execute's a command when resource is updated or changed