Update changelogs from fern repo (#2459)

Co-authored-by: coltondotio <10538007+coltondotio@users.noreply.github.com>

Author: fern-support

fern/products/cli-api-reference/cli-changelog/2025-12-02.mdx

@@ -1,3 +1,10 @@
+## 2.17.0
+**`(feat):`** Add `substitute-env-vars` flag to `docs.yml` settings configuration. When set to `true`, 
+environment variables using `${VAR_NAME}` syntax are substituted across all files in the docs bundle,
+including markdown/MDX content. This is useful for injecting dynamic values like API keys or URLs.
+Use \$\{VAR\} to escape and output literal ${VAR} without substitution.
+
+
 ## 2.16.0
 **`(feat):`** Add support for aliases in generators.yml. You can now define aliases that map to multiple groups, allowing you to run multiple groups with a single command.