Docs: add example for root domain delegation

- Change link in README to internal documentation link; original more
  detailed link is preserved in documentation page as a reference.
- Add Caddy example.

TODO:
- [x] Add example for Caddy
- [ ] Add example for Traefik

README.md

@@ -51,7 +51,7 @@ This is just a summary for the impatient. See the full
 [documentation](https://matrix-construct.github.io/tuwunel/).
 
 > [!TIP]
-> Avoid using a sub-domain for your `server_name`. You can always delegate later with a [`.well-known`](https://github.com/spantaleev/matrix-docker-ansible-deploy/blob/master/docs/configuring-well-known.md)
+> Avoid using a sub-domain for your `server_name`. You can always delegate later with a [`.well-known`](https://matrix-construct.github.io/tuwunel/deploying/root-domain-delegation.html)
 > file, but you can never change your `server_name`.
 
 **2.** Setup TLS certificates. Most users enjoy the [Caddy](https://caddyserver.com/) reverse-proxy

docs/deploying/root-domain-delegation.md

@@ -92,11 +92,28 @@ At a minimum, the following JSON files should be created:
 
 ### Option 2: Reverse proxy
 
-This is an example configuration if `example.com` is reverse-proxied behing Nginx.
+These are example configurations if `example.com` is reverse-proxied behing Nginx or Caddy.
 
 > [!NOTE]  
 > Replace `tuwunel` with the URL where tuwunel is listening; this may look like `127.0.0.1:8008`, `matrix.example.com`, or `tuwunel` if you declared an `upstream tuwunel` block.
 
+> [!IMPORTANT]  
+> These configurations need to be applied to the reverse proxy for `example.com`, **not** `matrix.example.com`.
+
+#### Caddy
+
+<!-- from https://github.com/spantaleev/matrix-docker-ansible-deploy/blob/c9bb48ff110dfca73946c69780ef8633e87b22f9/docs/configuring-well-known.md?plain=1#L150,L156 -->
+
+```caddy
+example.com {
+	reverse_proxy /.well-known/matrix/* https://matrix.example.com {
+		header_up Host {upstream_hostport}
+	}
+}
+```
+
+#### Nginx
+
 ```nginx,hidelines=~
 server {
   ~listen 443 ssl http2;
@@ -116,3 +133,9 @@ server {
 ## Testing
 
 Navigate to `example.com/.well-known/matrix/client` and `example.com/.well-known/matrix/server`. These should display results similar to the [JSON snippets above](#option-1-static-json-files).
+
+Entering `example.com` in the [Matrix federation tester](https://federationtester.matrix.org/) should also work.
+
+## Additional resources
+
+For a more complete guide, see the Matrix setup with Ansible and Docker [documentation on setting up `.well-known`](https://github.com/spantaleev/matrix-docker-ansible-deploy/blob/master/docs/configuring-well-known.md).