Add Caddy 2 example (#7463)

The specific headers that are passed using this new configuration format
are Host and X-Forwarded-For, which should be all that's required.

Note that for production another matcher should be added in the first
section to properly handle the base_url lookup:
reverse_proxy /.well-known/matrix/* http://localhost:8008

Signed-off-by: Jeff Peeler <jpeeler@gmail.com>

changelog.d/7463.doc

@@ -0,0 +1 @@
+Add additional reverse proxy example for Caddy v2. Contributed by Jeff Peeler.

docs/reverse_proxy.md

@@ -62,7 +62,7 @@ the reverse proxy and the homeserver.
 > **NOTE**: Do not add a `/` after the port in `proxy_pass`, otherwise nginx will
 canonicalise/normalise the URI.
 
-### Caddy
+### Caddy 1
 
         matrix.example.com {
           proxy /_matrix http://localhost:8008 {
@@ -76,6 +76,16 @@ canonicalise/normalise the URI.
           }
         }
 
+### Caddy 2
+
+        matrix.example.com {
+          reverse_proxy /_matrix/* http://localhost:8008
+        }
+
+        example.com:8448 {
+          reverse_proxy http://localhost:8008
+        }
+
 ### Apache
 
         <VirtualHost *:443>