Fix default HighlightCodeBlock fn: Write tags on separate lines

org/html.go

@@ -34,7 +34,7 @@ var listTags = map[string][]string{
 func NewHTMLWriter() *HTMLWriter {
 	return &HTMLWriter{
 		HighlightCodeBlock: func(source, lang string) string {
-			return fmt.Sprintf(`<div class="highlight">%s<pre>%s</pre>%s</div>`, "\n", html.EscapeString(source), "\n")
+			return fmt.Sprintf("%s\n<pre>\n%s\n</pre>\n</div>", `<div class="highlight">`, html.EscapeString(source))
 		},
 	}
 }

org/testdata/blocks.html

@@ -1,19 +1,23 @@
 <div class="captioned">
 <div class="highlight">
-<pre>echo &#34;a bash source block&#34;
+<pre>
+echo &#34;a bash source block&#34;
 
 function hello {
     echo Hello World!
 }
 
-hello</pre>
+hello
+</pre>
 </div>
 <p class="caption">
 block caption
 </p>
 </div>
 <div class="highlight">
-<pre>a source block without a language</pre>
+<pre>
+a source block without a language
+</pre>
 </div>
 <pre class="example">
 an example block with

org/testdata/captions.html

@@ -3,7 +3,9 @@ Anything can be captioned. Also captions are not real, correct captions but just
 </p>
 <div class="captioned">
 <div class="highlight">
-<pre>echo &#34;i have a caption!&#34;</pre>
+<pre>
+echo &#34;i have a caption!&#34;
+</pre>
 </div>
 <p class="caption">
 captioned soure block

org/testdata/footnotes.html

@@ -41,7 +41,9 @@ and other elements
 like blocks
 </p>
 <div class="highlight">
-<pre>other non-plain</pre>
+<pre>
+other non-plain
+</pre>
 </div>
 </li>
 <li>

org/testdata/lists.html

@@ -49,7 +49,9 @@ and some lines of text
 and another subitem
 </p>
 <div class="highlight">
-<pre>echo with a block</pre>
+<pre>
+echo with a block
+</pre>
 </div>
 </li>
 <li>