Update documentation and configuration for Realtime Agent Studio

- Revised mkdocs.yml to reflect the new site name and description, enhancing clarity for users.
- Added a changelog.md to document important changes and updates for the project.
- Introduced a roadmap.md to outline development plans and progress for future releases.
- Expanded index.md with a comprehensive overview of the platform, including core features and installation instructions.
- Enhanced concepts documentation with detailed explanations of assistants, engines, and their configurations.
- Updated configuration documentation to provide clear guidance on environment setup and service configurations.
- Added extra JavaScript for improved user experience in the documentation site.

docs/overrides/main.html

@@ -0,0 +1,9 @@
+{% extends "base.html" %}
+
+{% block extrahead %}
+  <meta name="author" content="RAS Team">
+  <meta name="keywords" content="AI, Voice Agent, Realtime, LLM, ASR, TTS, WebSocket">
+  <meta property="og:title" content="{{ page.title }} - Realtime Agent Studio">
+  <meta property="og:description" content="构建实时交互音视频智能体的开源工作平台">
+  <meta property="og:type" content="website">
+{% endblock %}