add documentation to allow access by IP address rather than hostname.

[dalf]

It seems some users want to use an IP address rather an hostname.

Currently this fail:

searxng-docker/.env

Lines 6 to 7 in f2f9e2a

	# SEARXNG_HOSTNAME=<host>
	# LETSENCRYPT_EMAIL=<email>

searxng-docker/docker-compose.yaml

Lines 14 to 15 in f2f9e2a

	- SEARXNG_HOSTNAME=${SEARXNG_HOSTNAME:-http://localhost:80}
	- SEARXNG_TLS=${LETSENCRYPT_EMAIL:-internal}

searxng-docker/Caddyfile

Lines 5 to 10 in f2f9e2a

	{$SEARXNG_HOSTNAME} {
	log {
	output discard
	}
	tls {$SEARXNG_TLS}

The last block looks something like

 10.0.0.1 { 
   log { 
         output discard 
   } 
  
   tls internal # <--- this line should be here for an IP address

I'm not sure if all the setup can be done in .env, but we can add documentation to remove the tls {$SEARXNG_TLS} line.