Adds SDK and curl options for the preview branch targeting

Author: samejr

docs/management/authentication.mdx

@@ -100,7 +100,26 @@ await envvars.upload("proj_1234", "dev", {
 
 When working with preview branches, you may need to target a specific branch when making API calls. This is particularly useful for managing environment variables or other resources that are scoped to individual preview branches.
 
-To target a specific preview branch, include the `x-trigger-branch` header in your API requests with the branch name as the value:
+<Tabs>
+  <Tab title="SDK">
+    To target a specific preview branch, include the `previewBranch` option in your SDK configuration:
+
+```ts
+import { configure, envvars } from "@trigger.dev/sdk";
+
+configure({
+  secretKey: process.env["TRIGGER_ACCESS_TOKEN"], // starts with tr_pat_
+  previewBranch: "feature-xyz",
+});
+
+await envvars.update("proj_1234", "preview", "DATABASE_URL", {
+  value: "your_preview_database_url",
+});
+```
+
+  </Tab>
+  <Tab title="cURL">
+    To target a specific preview branch, include the `x-trigger-branch` header in your API requests with the branch name as the value:
 
 ```bash
 curl --request PUT \
@@ -112,7 +131,8 @@ curl --request PUT \
     "value": "your_preview_database_url"
   }'
 ```
-
+  </Tab>
+</Tabs>
 This will set the `DATABASE_URL` environment variable specifically for the `feature-xyz` preview branch.
 
 <Note>