Total blocked hosts counter

Have a question or an idea? Please search it [on our forum](https://github.com/AdguardTeam/AdGuardHome/discussions) to make sure it was not yet asked. If you cannot find what you had in mind, please [submit it here](https://github.com/AdguardTeam/AdGuardHome/discussions/new).

### Prerequisites

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

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

### Problem Description
I never know exactly how many hosts are blocked

### Proposed Solution

Add a counter that counts all blocked hosts together and then add it to the dashboard