docs: enabled nginx syntax highlighting

docs/nginx-proxy.md

@@ -2,7 +2,7 @@
 
 Example of nginx configuration (reverse proxy) running remark42 service on remark42.example.com
 
-```
+```nginx
 server {
     listen      443;
     server_name remark42.example.com;
@@ -47,4 +47,4 @@ server {
 }
 ```
 
-note: `proxy_pass` points to internal DNS name `remark42` and expected to run from the same compose. If nginx runs outside of compose the real IP (or docker's bridge IP) should be used
+note: `proxy_pass` points to internal DNS name `remark42` and expected to run from the same compose. If nginx runs outside of compose the real IP (or docker's bridge IP) should be used