Update stack-seed.md

Author: shannona

_includes/stack-seed.md

@@ -5,6 +5,7 @@ _Much of Blockchain Commons' work is focused on providing users with secure & re
 * **Seeds.** Seeds are the foundation of digital-asset security, as they're used to generate signing keys and auth keys, often in a hierarchical manner. URs allow the encoding of seeds as `ur:seed`, but Envelopes are now preferred because they can store metadata and also allow for encryption or elision. Blockchain Commons' [seedtool-cli-rust](https://github.com/BlockchainCommons/seedtool-cli-rust) and [Seedtool for iOS](https://github.com/BlockchainCommons/GordianSeedTool-iOS) offer best practices for the management of seeds.
     * See our [128-bit test seed](/seed-128/)
     * See our [256-bit test seed](/seed-256/)
+    * See [Envelopes in seeds](/envelope/seed/)
 
 * **Entropy.** The randomness used to create seeds is Entropy.