Added link to OIDC docs in .env.example.complete

.env.example.complete

@@ -134,7 +134,7 @@ STORAGE_S3_ENDPOINT=https://my-custom-s3-compatible.service.com:8001
 STORAGE_URL=false
 
 # Authentication method to use
-# Can be 'standard', 'ldap' or 'saml2'
+# Can be 'standard', 'ldap', 'saml2' or 'oidc'
 AUTH_METHOD=standard
 
 # Social authentication configuration
@@ -242,6 +242,7 @@ SAML2_GROUP_ATTRIBUTE=group
 SAML2_REMOVE_FROM_GROUPS=false
 
 # OpenID Connect authentication configuration
+# Refer to https://www.bookstackapp.com/docs/admin/oidc-auth/
 OIDC_NAME=SSO
 OIDC_DISPLAY_NAME_CLAIMS=name
 OIDC_CLIENT_ID=null