Copy Button Doesn't Work in WebGL

[skibitsky]

Describe the bug
The copy uri button of WalletConnect Modal doesn't work in WebGL

To Reproduce
Steps to reproduce the behavior:

1. Go to https://wcm-unity.vercel.app
2. Select any network
3. Click on the Copy button at the top left corner
4. See Link copied notification, but no URI in the copy buffer

Environment

• Unity version: 2021.3.22f1
• Package name and version: WalletConnectUnity Modal v1.0.6

Additional context
Unity does't seem to support GUIUtility.systemCopyBuffer in WebGL. Need to bridge it through JS.