Add preview feature toggle guidance to CLI configuration docs

src/frontend/src/content/docs/reference/cli/configuration.mdx

@@ -50,6 +50,30 @@ can configure.
   installed CLI as the authoritative source for what can be configured.
 </Aside>
 
+## Toggle preview feature experiences
+
+Use feature flags to opt in to preview experiences that your installed Aspire
+CLI supports.
+
+1. Run `aspire config list --all` to discover available `features.*` keys.
+
+2. Enable a feature flag for the current project with `aspire config set`:
+
+   ```bash title="Enable a project-scoped preview feature"
+   aspire config set features.<featureKey> true
+   ```
+
+3. Use `--global` when you want the feature enabled by default across projects.
+   Copy the key name exactly from `aspire config list --all` because some
+   language-specific flags use a `:<language>` suffix:
+
+   ```bash title="Enable a user-scoped preview feature default"
+   aspire config set features.<featureKey> true --global
+   ```
+
+4. Turn a feature off by setting it to `false`, or remove the override with
+   `aspire config delete <key>`.
+
 ## Working with configuration
 
 - Use `aspire config list` to show currently set project-scoped and global