Feature Request: Add Manual Installation Instructions

### Issue Details

I would like to request the addition of manual installation instructions for the AdGuard VPN CLI. While the automated installer is convenient, having a manual installation option would be beneficial for users who prefer or require more control over the installation process. This could help users with specific system configurations or environments where automated scripts are restricted.

### Proposed solution

Please consider adding a section in the documentation that outlines the steps for manual installation, including any prerequisites, commands, and configuration options. This would enhance the usability of the AdGuard VPN CLI for a broader range of users.

### Alternative solution

_No response_