Update `manifest.json` for Progressive Web App (PWA) Integration

Context:

PWAs offer better offline functionality, improved performance, and can be installed on users' devices. Currently, it has a default manifest.json. Let's update it to make relevant PWA configuration.

• Here's the website: 50daysofjavascript.netlify.app
• Learn more about PWAs.

Proposed Changes:

• Description: Adding a description field to provide a brief overview of our website.

• Theme Color: Changing the theme color to match our branding and improve the appearance of the PWA when added to the home screen.

• Scope: Setting the scope to "/", so the PWA works for all pages of our website.

• Orientation: Specifying "portrait" as the default orientation to ensure a consistent user experience.

• Additional Icons: Adding a 512x512 icon for better quality on high-resolution devices.