Updated the logo, added the favicon and added a gemini note to custom… (#394)

… llms

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **New Features**
* Added a custom favicon to the generated HTML documentation for
improved branding.

* **Documentation**
* Updated documentation to include "Google Gemini" as an example of a
custom LLM provider that can be added via API keys.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Author: jairovelasquez

source/_static/favicon.ico

@@ -234,4 +234,5 @@
 ]
 
 html_logo = "_static/logo-white.svg"
+html_favicon = "_static/favicon.ico"
 html_extra_path = ['robots.txt']

source/_static/img/favicon.ico

@@ -29,7 +29,7 @@ We support the following providers:
 Custom LLM Providers
 ====================
 
-You can add a custom LLM provider in Codio by entering API keys on the **Organization** > **LLMs** page. This allows you to use your chosen LLM provider in your courses.
+You can add a custom LLM provider, such as Google Gemini, to Codio by entering the API keys on the **Organization** > **LLMs** page. This allows you to use your chosen LLM provider in your courses.
 
 .. image:: /img/custom_llm_provider.png
        :alt: Custom LLM Providers

source/_static/logo-white.svg

@@ -235,4 +235,5 @@
 ]
 
 html_logo = "_static/logo-white.svg"
+html_favicon = "_static/favicon.ico"
 html_extra_path = ['robots.txt']