feat: Add custom timeout to LS Duo chat

Description

It adds a custom timeout for the LS Chat load.

On the slower network 10 seconds might not be enough for the chat to load.

How has this been tested?

1. Set the extension setting to some tiny value "gitlab.webviewTimeoutSeconds": 0.01
2. Update the check interval to 10 here. Because after 200ms chat might be already loaded 3.Open Duo chat - you should see the error screen instead of chat
3. Run extension and open duo chat

Screenshots (if appropriate)

What CHANGELOG entry will this MR create?

• fix: Bug fix fixes - a user-facing issue in production - included in changelog
• feature: New feature - a user-facing change which adds functionality - included in changelog
• BREAKING CHANGE: (fix or feature that would cause existing functionality to change) - should bump major version, mentioned in the changelog
• None - other non-user-facing changes