Updated Setup (markdown)

Setup.md

@@ -8,6 +8,8 @@
 <li><a href="#nginx-variable">Nginx Variable</a></li>
 <li><a href="#apache">Apache</a></li>
 <li><a href="#caddy">Caddy</a></li>
+<li><a href="#caddy-v2">Caddy V2</a></li>
+
 </ul>
 </li>
 <li><a href="#stylus-method">Stylus Method</a></li>
@@ -208,6 +210,108 @@ $.getScript('https://archmonger.github.io/Blackberry-Themes/Extras/theme_install
 });
 ```
 
+### Caddy v2
+
+We rely on sjtug's [caddy2-filter](https://github.com/sjtug/caddy2-filter) as Caddy v2 does not have filtering as of now.
+
+There are two ways to [extend Caddy](https://caddyserver.com/docs/extending-caddy):
+
+- [Docker](https://hub.docker.com/_/caddy)
+- [Bare metal](https://caddyserver.com/docs/download)
+
+### Docker
+
+You will have to create your own Caddy image that includes the `caddy2-filter`.
+
+`Dockerfile`:
+
+```
+FROM caddy:2.0.0-builder AS builder
+
+RUN caddy-builder \
+    github.com/sjtug/caddy2-filter
+
+FROM caddy:2.0.0
+
+COPY --from=builder /usr/bin/caddy /usr/bin/caddy
+```
+
+Then run `docker build -t caddy:latest .` to build the image. After we update the `Caddyfile` below, we can (re)start the container by running `docker run -d -p 80:80 -p 443:443 caddy:latest` as an example.
+
+### Bare metal
+
+Make sure you install [xcaddy](https://github.com/caddyserver/xcaddy) to add modules to Caddy.
+
+Then install the `caddy2-filter` module by using:
+
+```sh
+xcaddy build \
+    --with github.com/sjtug/caddy2-filter
+```
+
+You can confirm the module is available by using `xcaddy list-modules`.
+
+### Updating the `Caddyfile`
+
+Almost like Caddy v1, here is an example `filter` we need to include in the all the services we want themed:
+
+```
+filter {
+	content_type text/html.*
+	search_pattern </head>
+	replacement "<link rel='stylesheet' type='text/css' href='https://gilbn.github.io/theme.park/CSS/themes/<APP_NAME>/<THEME>.css'></head>"
+}
+```
+
+With `caddy2-filter`, we need to also add this option in the global option block:
+
+```
+{
+	order filter after encode
+}
+```
+
+And if you're using a reverse proxy, you also need to include `header_up -Accept-Encoding` in the `reverse_proxy` directive body.
+
+<details>
+<summary>Full example of a Caddyfile</summary>
+
+```
+{
+	order filter after encode
+}
+
+radarr.example.com {
+	encode zstd gzip
+	reverse_proxy 127.0.0.1:7878 {
+		header_up -Accept-Encoding
+	}
+	filter {
+		content_type text/html.*
+		search_pattern </head>
+		replacement "<link rel='stylesheet' type='text/css' href='https://gilbn.github.io/theme.park/CSS/themes/radarr/space-gray.css'></head>"
+	}
+}
+```
+
+</details>
+
+> :point_right: If your service requires you to ignore a header, use the `header_down` subdirective in the `reverse_proxy` directive. For example, qBittorrent usage would look like this:
+
+```
+reverse_proxy 127.0.0.1:8080 {
+	header_up -Accept-Encoding
+	header_down -x-webkit-csp
+	header_down -content-security-policy
+}
+```
+
+---
+
+Feel free to make any adjustments! Thanks everyone for the help!
+
+Also for reference: [Caddy v2 structure](https://caddyserver.com/docs/caddyfile/concepts#structure)
+
 # Qbittorrent
 
 As Qbittorrent will block the theme with its content security policy you need to change or remove the CSP header.