Create a Dockerfile for Hysteria client, with wiki in the README

[Winson-030]

Hi Teddy,

I appreciate your work on this repo. I recently attempted to deploy a Hysteria client container in my homelab but noticed only a server image was available. To address this, I've created a Dockerfile for the Hysteria client and added it to the repo along with an explanatory wiki in the README.

Hopefully, this will assist others looking to deploy a Hysteria client container.

WinsonLee