docs: update node and deno requirements in dev guidelines

[rishika-2626]

Description

Updated the development guidelines to reflect the current technical requirements for the 2026 build.

Changes:

• Updated Node.js requirement to v22.16.0.
• Added Deno as a core requirement for the Apps-Engine.
• Included corepack enable in the setup steps to ensure Yarn 4 support.
• Removed outdated references to Fibers and Node 14.

These changes match the actual environment needed to run the current develop branch of Rocket.Chat.

Checklist

• [x] Tested the steps on my local machine.
• [x] Verified Node and Deno versions.
• [x] Followed the repository's contribution guidelines.