Cannot report a website from Assistant when UI is not running

[ameshkov]

Original report:
AdguardTeam/AdguardAssistant#194

Steps to reproduce

1. Tray menu -> "Close Adguard but continue filtering"
2. Open example.org
3. Open Assistant and click "Report website"

Expected behavior

The report website is opened.

Actual behavior

Nothing happens.

Proposed solution

Change the ADG_sendAbuse implementation. Instead of opening a new website, send a message to the service side and receive a report URL, then simply call window.open.