Add changelog for 2025-06-18 (#521)

Author: quantstruct-bot

fern/changelog/2025-06-18.mdx

@@ -0,0 +1,15 @@
+## Overview
+
+1. **API Request Tool**: You can now create [API request tools](https://api.vapi.ai/api#:~:text=ApiRequestTool) that allow the assistant to make REST API calls during conversations
+
+  <Frame caption="Make GET or POST requests to any API in your workflows">
+    <img src="../static/images/changelog/api-request-tool.png" />
+  </Frame>
+
+2. **Specify GCP Region**: You can now specify the region for your [GCP Credentials](https://dashboard.vapi.ai/settings/integrations#:~:text=Save-,GCP%20credentials,-For%20storing%20the), This gives you control over where your call artifacts are stored.
+
+  <Frame caption="Specify the region for your GCP Credentials">
+    <img src="../static/images/changelog/gcp-credentials-region.png" />
+  </Frame>
+
+3. **Transcriber Formatting Option**: A new `formatTurns` option in your [`Assembly AI Transcriber`](https://api.vapi.ai/api#:~:text=AssemblyAITranscriber) that lets you enable or disable formatting of transcripts when using AssemblyAI's Universal Streaming API. This helps you format transcript outputs to show speaker turns.