lazy loading

[rushabhpanbude]

1. implemented lazy loading
2. fixed css display flex issue with sidebar

Related Issue

Closes: #516

Description of Changes

Checklist:

• [X] My code adheres to the established style guidelines of this project.
• [X] I have conducted a self-review of my code.
• [X] I have included comments in areas that may be difficult to understand.
• [X] I have made corresponding updates to the project documentation.
• [X] My changes have not introduced any new warnings.

Screenshots

Original	Updated

Please provide any necessary screenshots to illustrate the changes made.