feat: Added KaTeX icon/button to chat toolbar for documentation access

[KrishnaShuk]

Added KaTeX Documentation Button to Chat Input Toolbar

This PR adds a KaTeX icon/button to the chat input formatting toolbar. Clicking the button will open the KaTeX documentation in a new tab, making it easier for users to reference formatting syntax.

This update ensures the toolbar section aligns with the Rocket.Chat server's toolbox design.

Acceptance Criteria fulfillment

• [ ] 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.

Fixes #985

Video/Screenshots

Screencast from 2025-02-13 20-21-56.webm

PR Test Details

Note: The PR will be ready for live testing at https://rocketchat.github.io/EmbeddedChat/pulls/pr-<pr_number> after approval. Contributors are requested to replace <pr_number> with the actual PR number.

[KrishnaShuk]

There is some issue in katex rendering. PR #977 is made for solving this issue.