feat: support for KV version 1 and custom-named engines (#12)

* feat: kv v1 and engine path

* doc: add custom version and engine path usage docs

Co-authored-by: Richard Simpson <richardsimpson@outlook.com>

README.md

@@ -1,6 +1,8 @@
 # vault-action
 
-A helper action for easily pulling secrets from the default v2 K/V backend of vault.
+A helper action for easily pulling secrets from the K/V backend of vault.
+
+Expects [Version 2](https://www.vaultproject.io/docs/secrets/kv/kv-v2/) of the KV Secrets Engine by default.
 
 ## Example Usage
 
@@ -39,7 +41,7 @@ with:
   url: https://vault.mycompany.com:8200
   method: approle
   roleId: ${{ secrets.roleId }}
-  secretId : ${{ secrets.secretId }}
+  secretId: ${{ secrets.secretId }}
 ```
 
 ## Key Syntax
@@ -93,9 +95,33 @@ with:
         ci/aws secretKey | AWS_SECRET_ACCESS_KEY
 ```
 
+### Using K/V version 1
+
+By default, `vault-action` expects a K/V engine using [version 2](https://www.vaultproject.io/docs/secrets/kv/kv-v2.html).
+
+In order to work with a [v1 engine](https://www.vaultproject.io/docs/secrets/kv/kv-v1/), the `kv-version` parameter may be passed:
+
+```yaml
+with:
+    kv-version: 1
+```
+
+### Custom Engine Path
+
+When you enable the K/V Engine, by default it's placed at the path `secret`, so a secret named `ci` will be accessed from `secret/ci`. However, [if you enabled the secrets engine using a custom `path`](https://www.vaultproject.io/docs/commands/secrets/enable/#inlinecode--path-4), you
+can pass it as follows:
+
+```yaml
+with:
+    path: my-secrets
+    secrets: ci npmToken
+```
+
+This way, the `ci` secret in the example above will be retrieved from `my-secrets/ci`.
+
 ### Namespace
 
-This action could be use with namespace Vault Enterprise feature. You can specify namespace in request : 
+This action could be use with namespace Vault Enterprise feature. You can specify namespace in request :
 
 ```yaml
 steps: