Updated for v2.8.0 (#389)

Co-authored-by: Mohammed Al Sahaf <msaa1990@gmail.com>
Co-authored-by: Francis Lavoie <lavofr@gmail.com>
Co-authored-by: Nebez Briefkani <me@nebezb.com>
Co-authored-by: Mohammed Al Sahaf <mohammed@caffeinatedwonders.com>

src/docs/markdown/caddyfile/directives/fs.md

@@ -0,0 +1,48 @@
+---
+title: fs (Caddyfile directive)
+---
+
+# fs
+
+Sets which file system should be used for performing file I/O.
+
+This could let you connect to a remote filesystem running in the cloud, or a database with a file-like interface, or even to read from files embedded within the Caddy binary.
+
+First, you must declare a file system name using the [`filesystem` global option](/docs/caddyfile/options#filesystem), then you can use this directive to specify which file system to use.
+
+This directive is often used in conjunction with the [`file_server` directive](file_server) to serve static files, or the [`try_files` directive](try_files) to perform rewrites based on the existence of files. Typically also used with [`root` directive](root) to set the root path within the file system.
+
+
+## Syntax
+
+```caddy-d
+fs [<matcher>] <filesystem>
+```
+
+## Examples
+
+Using an file system named `foo`, using an imaginary module named `custom` which might require authentication:
+
+```caddy
+{
+	filesystem foo custom {
+		api_key abc123
+	}
+}
+
+example.com {
+	fs foo
+	root /srv
+	file_server
+}
+```
+
+To only serve images from the `foo` file system, and the rest from the default file system:
+
+```caddy
+example.com {
+	fs /images* foo
+	root /srv
+	file_server
+}
+```