v1.2.0: implements Gemini and Grok Clients

This new release implements a client for Gemini and for Grok.
Note: The Gemini client has been tested, but not the Grok client because the Grok API is not yet available in my country.
If you have problems with Grok, please open a GitHub issue and describe it, I'll try to fix it in a blind way.

What's Changed

• implement a client for Gemini by @leolivier in #6
• Leolivier/issue3 by @leolivier in #7

Full Changelog: v1.1.0...v1.2.0