Fixes/666 Add Keyboard Shortcut Guide and Custom Scrollbar

[manask-pradhan]

PR Fixes:

• 1 #665
• 2 #666

Resolves #665 Resolves #666

• Implemented a pop-up window to display keyboard shortcuts for the video player.
• Included navigation links to important sections of the application.

Checklist before requesting a review

• [x] I have performed a self-review of my code
• [x] I assure there is no similar/duplicate pull request regarding same issue

[manask-pradhan]

@hkirat sir, please check this feature

[manask-pradhan]

To fix this, i created another PR