Add blocking mode that displays an errorpage

[phixion]

Sorry if duplicate - I couldnt find a feature request for this.

Not many people understand when their browser yells NXDOMAIN at them, so they raise questions.

• Present user a Blockingpage pulled from the webserver that adguard runs anyway.

• Show the user what filterled to his/her block and maybe give ability to (request a) whitelist the domain.

• Maybe even more aditional statistics about the client.

• Evaluate performance impact/overhead of serving those pages to X amount of clients.

[Onepamopa]

That won't work for HTTPS connections, since the certificate (if any) won't match.

[CYAsistemas]

Or add a option to render al self html contained in adguardhome