Add 'Open in IDX' button

Plus minor updates to `README.md`

Author: fredsa

README.md

@@ -4,14 +4,23 @@ Developer sample written in Angular, demonstrating how to use the Gemini API and
 function calling to collaboratively and iteratively create a database schema
 using natural language prompts.
 
-
-Caution: Using the Google AI SDK directly from a client-side app as is shown in
-this sample is recommended for prototyping only. For non-prototyping use cases,
-we strongly recommend that you call the Google AI Gemini API only server-side to
-keep your API key safe. If you embed your API key directly in your web app or
-fetch it remotely at runtime, you risk potentially exposing your API key to
-malicious actors.
-
+<a href="https://idx.google.com/import?url=https://github.com/google-gemini/angular-database-schema-sample">
+<picture>
+  <source media="(prefers-color-scheme: dark)" srcset="https://cdn.idx.dev/btn/[email protected]">
+  <source media="(prefers-color-scheme: light)" srcset="https://cdn.idx.dev/btn/[email protected]">
+  <img height="32" alt="Open in IDX" src="https://cdn.idx.dev/btn/[email protected]">
+</picture>
+</a>
+
+## Usage notes
+
+> [!CAUTION]
+> Using the Google AI SDK directly from a client-side app as is shown in
+> this sample is recommended for prototyping only. For non-prototyping use
+> cases, we strongly recommend that you call the Google AI Gemini API only
+> server-side to keep your API key safe. If you embed your API key directly in
+> your web app or fetch it remotely at runtime, you risk potentially exposing
+> your API key to malicious actors.
 
 This project was initially generated with
 [Angular CLI](https://github.com/angular/angular-cli) version 17.0.5.