Add nginx config for acme challenge

What does this MR do?

Adds Nginx config to allow for acme challenges, for services such as LetsEncrypt

Are there points in the code the reviewer needs to double check?

That there are no Nginx syntax errors and starts correctly

Why was this MR needed?

LetsEncrypt is becoming more popular and currently to use it you either need to manually change the Nginx config, or stop GitLab to free up port 80.

Does this MR meet the acceptance criteria?

What are the relevant issue numbers?