feat: added screen sharing support

[ADARSHsri2004]

Description

This PR adds full screen sharing support to the PeerCall application for one-to-one WebRTC calls.
The feature is implemented entirely within the InRoom.tsx file and integrates smoothly with the existing WebRTC + Socket.IO signaling architecture.

Key Features Implemented

1. Screen Sharing

• Added ability for a user to share their screen during a call using navigator.mediaDevices.getDisplayMedia().
• The shared screen replaces the camera video stream in the active RTCPeerConnection.
• When screen sharing stops (either manually or through browser “Stop sharing”), the app automatically switches back to the user’s camera stream.

2. Stream Replacement Logic

• Implemented proper sender.replaceTrack() logic to dynamically switch between:
• Camera video track
• Screen share video track
• No renegotiation required; remote peer immediately receives the updated video track

3. Stable One-to-One WebRTC Flow

• Cleaned and simplified entire 1:1 call pipeline:
• Local media capture
• PeerConnection creation
• Offer/Answer exchange
• ICE candidate exchange
• Remote track event handling

4. UI Updates

• Added clear buttons for:
• Start Screen Share
• Stop Screen Share
• Updated local video tile to visually reflect when screen sharing is active.

Semver Changes

• Patch (bug fix, no new features)
• Minor (new features, no breaking changes)
• Major (breaking changes)

Issues

Closes #4

Checklist

• I have read the Contributing Guidelines.