reverse_proxy: add health_follow_redirects (#401)

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

@@ -72,6 +72,7 @@ reverse_proxy [<matcher>] [<upstreams...>] {
 	health_timeout  <duration>
 	health_status   <status>
 	health_body     <regexp>
+	health_follow_redirects
 	health_headers {
 		<field> [<values...>]
 	}
@@ -324,6 +325,8 @@ Active health checks perform health checking in the background on a timer. To en
 
 - **health_body** <span id="health_body"/> is a substring or regular expression to match on the response body of an active health check. If the backend does not return a matching body, it will be marked as down.
 
+- **health_follow_redirects** <span id="health_follow_redirects"/> will cause the health check to follow redirects provided by upstream. Without this setting, a redirect will cause the check to fail.
+
 - **health_headers** <span id="health_headers"/> allows specifying headers to set on the active health check requests. This is useful if you need to change the `Host` header, or if you need to provide some authentication to your backend as part of your health checks.