[configuration] only perform replacement on resources which content type is text

[IceCodeNew]

My ISP blocks the site mikanani.me, and I am trying to set up a reverse proxy for it. Thanks for this great project; I managed to make it work.
Based on a working configuration, I took a step further to lower the memory consumption so this mirror site could handle a crowd of users. And that is where I came into a problem.
The only change between a working configuration and a broken one is to enable a response matcher. But no matter how hard I tried, I couldn't understand what happened. Any information would be appreciated.

The site being proxied is very simple, and there are no third-party resources to be loaded (except for its site icon): https://mikanani.me/RSS/Bangumi?bangumiId=3598&subgroupid=370
And here is the minimum reproducible bad configuration of my mirror site. No replacement performed with that configuration.

# broken configuration
{
	admin off
	debug
	storage file_system /usr/local/etc/caddy/
}

(extendable-proxy) {
	route {
		@text_content {
			header Content-Type application/javascript*
			header Content-Type application/json*
			header Content-Type application/xml*
			header Content-Type text/*
		}

		encode
		replace @text_content stream {
			{args[0]} {args[1]}
		}

		reverse_proxy https://{args[0]} {
			header_up Accept-Encoding identity
			header_up Host {upstream_hostport}
			header_up -X-Forwarded-*
			header_down Location {args[0]} {args[1]}
		}
	}
}

import sites-enabled/*

# sites-enabled/rp-to-mikan
aaa.example.com {
	import extendable-proxy mikanani.me aaa.example.com
}

# working configuration
- 		@text_content {
- 			header Content-Type application/javascript*
- 			header Content-Type application/json*
- 			header Content-Type application/xml*
- 			header Content-Type text/*
- 		}

		encode
- 		replace @text_content stream {
+ 		replace stream {