chore(readme): adding readme for hashicorp#440

Author: saipranav

README.md

@@ -19,6 +19,8 @@ A helper action for easily pulling secrets from HashiCorp Vault™.
     - [GitHub](#github)
     - [JWT with OIDC Provider](#jwt-with-oidc-provider)
     - [Kubernetes](#kubernetes)
+    - [Userpass](#userpass)
+    - [Ldap](#ldap)
     - [Other Auth Methods](#other-auth-methods)
   - [Key Syntax](#key-syntax)
     - [Simple Key](#simple-key)
@@ -256,6 +258,40 @@ with:
   kubernetesTokenPath: /var/run/secrets/kubernetes.io/serviceaccount/token # default token path
 ```
 
+### Userpass
+
+The [Userpass auth method](https://developer.hashicorp.com/vault/docs/auth/userpass) allows
+your GitHub Actions workflow to authenticate to Vault with a username and password.
+Set the username and password as GitHub secrets and pass them to the
+`username` and `password` parameters.
+
+This is not the same as ldap or okta auth methods.
+
+```yaml
+with:
+  url: https://vault.mycompany.com:8200
+  caCertificate: ${{ secrets.VAULT_CA_CERT }}
+  method: userpass
+  username: ${{ secrets.VAULT_USERNAME }}
+  password: ${{ secrets.VAULT_PASSWORD }}
+```
+
+### Ldap
+
+The [LDAP auth method](https://developer.hashicorp.com/vault/docs/auth/ldap) allows
+your GitHub Actions workflow to authenticate to Vault with a username and password inturn verfied with ldap servers.
+Set the username and password as GitHub secrets and pass them to the
+`username` and `password` parameters.
+
+```yaml
+with:
+  url: https://vault.mycompany.com:8200
+  caCertificate: ${{ secrets.VAULT_CA_CERT }}
+  method: ldap
+  username: ${{ secrets.VAULT_USERNAME }}
+  password: ${{ secrets.VAULT_PASSWORD }}
+```
+
 ### Other Auth Methods
 
 If any other method is specified and you provide an `authPayload`, the action will