docs: add ExpiresInMinutes as an email template variable (#2077)

Add ExpiresInMinutes as an email template variable

Author: TamerShlash

docs/kratos/emails-sms/05_custom-email-templates.mdx

@@ -243,6 +243,7 @@ For the `recovery_code.valid` template, the following variables are available:
 | `To` | The email address the email will be sent to |
 | `RecoveryCode` | The recovery code |
 | `Identity` | The identity to be recovered |
+| `ExpiresInMinutes` | The lifespan of the code, in minutes. |
 
 :::note