Wiki - Encryption - Certbot install unclear for docker image users

### Prerequisites

- [X] I have checked the [Wiki](https://github.com/AdguardTeam/AdGuardHome/wiki) and [Discussions](https://github.com/AdguardTeam/AdGuardHome/discussions) and found no answer

- [X] I have searched other issues and found no duplicates

- [X] I want to request a feature or enhancement and not ask a question

### The problem

**Using Certbot** chapter is too vague for users using the Adguard Home docker image.

The Certbot instruction doesn't seem to be available for alpine linux on which the Adguard Home docker image is based on.


### Proposed solution

Provide instruction on how to install certbot on the docker image.

### Alternatives considered and additional information

_No response_