chore: update changelog

Author: snakster

CHANGELOG.md

@@ -26,6 +26,8 @@ Given a version number `MAJOR.MINOR.PATCH`, we increment the:
 
 - Hide bundles in the `terrmate ui` promote list, if they reference other bundles that would not exist in the target environment.
   - This prevents errors that would otherwise occur once the bundle has been promoted.
+- Add support for `lets` block in bundles.
+  - The block is evaluated after bundle inputs and root attributes, but before exports and bundle stacks.
 
 ## 0.17.0