Userscripts support for AdGuard iOS

### Prerequisites

Please answer the following questions for yourself before submitting an issue. **YOU MAY DELETE THE PREREQUISITES SECTION.**

- [x] I am running the latest version
- [x] I checked the documentation and found no answer
- [x] I checked to make sure that this issue has not already been filed

### Problem Description

I'd like to have Userscripts support on iOS devices the same as in the macOS version.

### Proposed Solution

Implement support/management for Userscripts
https://developer.apple.com/documentation/webkit/wkusercontentcontroller/1538046-userscripts

### Alternatives Considered

AdGuard has no noteworthy alternatives ;)

### Additional Information