html: Render headline priority

org/html.go

@@ -197,6 +197,10 @@ func (w *HTMLWriter) writeHeadline(h Headline) {
 	if h.Status != "" {
 		w.WriteString(fmt.Sprintf(`<span class="todo">%s</span>`, h.Status) + "\n")
 	}
+	if h.Priority != "" {
+		w.WriteString(fmt.Sprintf(`<span class="priority">%s</span>`, h.Priority) + "\n")
+	}
+
 	w.WriteString(title)
 	if len(h.Tags) != 0 {
 		tags := make([]string, len(h.Tags))

org/testdata/headlines.html

@@ -3,6 +3,7 @@ Simple Headline
 </h1>
 <h1>
 <span class="todo">TODO</span>
+<span class="priority">B</span>
 Headline with todo status &amp; priority
 </h1>
 <h1>
@@ -13,6 +14,7 @@ Headline with TODO status
 the <strong>content</strong>
 </p>
 <h1>
+<span class="priority">A</span>
 Headline with tags &amp; priority&#xa0;&#xa0;&#xa0;<span class="tags"><span>foo</span>&#xa0;<span>bar</span></span>
 </h1>
 <p>