Document config parameters that are required for reverse HTTPS proxies

[MikeTheTux]

README.md documents only a part of the parameters that are required to setup Lychee 5.0 using a reverse HTTPS proxy.

According to LycheeOrg/Lychee#2103 (comment) the following was required in my case:

Lychee Docker:

• TRUSTED_PROXIES: *
• APP_URL: https://a.b.com:3444
• APP_FORCE_HTTPS: true

In /etc/nginx/nginx.conf of the lychee docker

• fastcgi_param HTTPS on;

Can /etc/nginx/nginx.conf be changed for for everyone as alternative?

Can you please extend README.md as well as https://hub.docker.com/r/lycheeorg/lychee with this info?

[ildyria]

@d7415 can you take care of this ? I don't know who has access to lycheeorg on github.