Add set up steps including nginx example

docs/how_to_setup_reverse_proxy

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+## Setting up reverse proxy
+To make Darawich work with a reverse proxy, you need to ensure the APPLICATION_HOST environment variable is set to the domain name that the reverse proxy will use.
+For example, if your Darawich instance is supposed to be on the domain name timeline.mydomain.com, then set the environment variable to "timeline.mydomain.com".
+Make sure to exclude "http://" or "https://" from the environment variable. The webpage will not work if you do include http:// or https:// in the variable.
+
+At the time of writing this, the way to set the environment variable is to edit the docker-compose.yml file. Find all APPLICATION_HOST entries in the docker-compose.yml file and change them from "localhost" to your domain name.
+For a synology install, refer to **[Synology Install Tutorial](docs/How_to_install_Dawarich_on_Synology.md)**. In this page it is explained how to set the APPLICATION_HOST environment variable.
+
+Now that the app works with a domain name, the server needs to be setup to use a reverse proxy. Usually this is done by setting it up in the virtual host configuration.
+
+Below are examples of reverse proxy configurations.
+
+### Nginx
+```
+server {
+	
+	listen 80;
+	listen [::]:80;
+	server_name example.com;
+	
+	location / {
+		proxy_set_header X-Real-IP $remote_addr;
+		proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+		proxy_set_header X-Forwarded-Proto https;
+		proxy_set_header X-Forwarded-Server $host;
+		proxy_set_header Host $http_host;
+		proxy_redirect off;
+    
+		proxy_pass http://127.0.0.1:3000/;
+	}
+
+}
+
+```