Unraid template available

[nwithan8]

Hello, I discovered this project the other day (very helpful!) and wrote an Unraid template for it so that Unraid users can easily install the Docker container from Unraid's Community App store. The template should be live in a few hours: https://unraid.net/community/apps?q=imgproxy#r

[DarthSim]

Hey @nwithan8!

I hadn't heard about Unraid before, so if you could open a PR with instructions on the template usage, I'd gladly merge it.