docs: added Documentation for Air-Gapped Installation

[badal773]

Description

Fixes #

Checklist:

• [ ] The title of the PR states what changed and the related issues number (used for the release note).
• [ ] Does this PR requires documentation updates?
• [ ] I've updated documentation as required by this PR.
• [ ] I have performed a self-review of my own code.
• [ ] I have commented my code, particularly in hard-to-understand areas.
• [ ] I have tested it for all user roles.
• [ ] I have added all the required unit/api test cases.

Does this PR introduce a user-facing change?