Switch to gemini-ai-sdk package for Google Gemini (#165)

gemini-g4f is now unmaintained. gemini-ai-sdk is the better, simpler way
to use Gemini AI, also maintained by me. It's been rewritten from
scratch, and it's so much simpler. More features coming soon.

New dependencies: gemini-ai-sdk, undici (for polyfill, since Raycast
doesn't support native fetch yet.)

Removed dependency: gemini-g4f

README.md

@@ -266,7 +266,7 @@ https://github.com/raycast/extensions/tree/main/extensions/raycast-gemini) by Ev
 Third-party libraries used for generation:
 
 - [g4f-image](https://www.npmjs.com/package/g4f-image)
-- [gemini-g4f](https://www.npmjs.com/package/gemini-g4f)
+- [gemini-ai-sdk](https://www.npmjs.com/package/gemini-ai-sdk)
 
 *(Both packages are maintained by the extension author.)*