feat: Adding a Katex documentation button

[KrishnaShuk]

As an EmbeddedChat developer

I need to:
Add a new icon/button on the Chat Input Formatting Toolbar.

So That:
Users can quickly access the KaTeX documentation in a new window.

This feature is implemented to ensure the toolbar section aligns with the Rocket.Chat server's toolbox.

Acceptance Criteria

• Add a KaTeX icon/button to the toolbar section.
• Ensure the button opens the official KaTeX documentation in a new tab or window when clicked.
• Maintain UI consistency with the existing toolbar design in Rocket.Chat.

Rocket Chat Toolbar

Embedded Chat Toolbar