Use a stylesheet for my RSS feed

Makefile

@@ -13,6 +13,7 @@ dev: serve rerun
 
 build:
 	cobalt build
+	./ext/add-feed-stylesheet.sh _site/feed.xml
 .PHONY: build
 
 serve:

ext/add-feed-stylesheet.sh

@@ -0,0 +1,10 @@
+#!/bin/bash
+
+{
+  echo '/<?xml'
+  printf 's/>/>\\\n/\n'
+  echo i
+  echo '<?xml-stylesheet href="/feed-style.xsl" type="text/xsl"?>'
+  echo .
+  echo w
+} | ed "$*" >/dev/null