Allow Markdown parser to recognize <aside> as an infobox declaration.

claat/parser/md/README.md

@@ -92,6 +92,18 @@ Negative
 : This will appear in a negative info box.
 ```
 
+`<aside>` elements work as well:
+
+```
+<aside class="positive">
+This will appear in a positive info box.
+</aside>
+
+<aside class="negative">
+This will appear in a negative info box.
+</aside>
+```
+
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claat/parser/md/html.go

@@ -92,6 +92,10 @@ func isButton(hn *html.Node) bool {
 	return hn.DataAtom == atom.Button
 }
 
+func isAside(hn *html.Node) bool {
+	return hn.DataAtom == atom.Aside
+}
+
 func isInfobox(hn *html.Node) bool {
 	if hn.DataAtom != atom.Dt {
 		return false

claat/parser/md/parse.go

@@ -354,6 +354,8 @@ func parseNode(ds *docState) (types.Node, bool) {
 		return code(ds, true), true
 	case isCode(ds.cur):
 		return code(ds, false), true
+	case isAside(ds.cur):
+		return aside(ds), true
 	case isInfobox(ds.cur):
 		return infobox(ds), true
 	case isSurvey(ds.cur):
@@ -535,6 +537,27 @@ func header(ds *docState) types.Node {
 	return n
 }
 
+// aside produces an infobox.
+func aside(ds *docState) types.Node {
+	kind := types.InfoboxPositive
+	for _, v := range ds.cur.Attr {
+		// If class "negative" is given, set the infobox type.
+		if v.Key == "class" && v.Val == "negative" {
+			kind = types.InfoboxNegative
+		}
+	}
+
+	ds.push(nil)
+	nn := parseSubtree(ds)
+	nn = blockNodes(nn)
+	nn = compactNodes(nn)
+	ds.pop()
+	if len(nn) == 0 {
+		return nil
+	}
+	return types.NewInfoboxNode(kind, nn...)
+}
+
 // infobox doesn't have a block parent.
 func infobox(ds *docState) types.Node {
 	negativeInfoBox := isInfoboxNegative(ds.cur)