Modify JATS reader to handle BITS too (#9138)

Add provision for title-group, book, book-part-wrapper, book-meta,
book-part-meta, book-title, book-title-group, index, toc, legend,
title, collection-meta

test/command/bits-index-elements.md

@@ -0,0 +1,83 @@
+```
+% pandoc -f jats -t native
+<index-group>
+	<index-title-group>
+		<title>Index group</title>
+	</index-title-group>
+	<p>Content of index group</p>
+	<index>
+		<index-title-group>
+			<title>Index</title>
+		</index-title-group>
+		<p>Content of index</p>
+  		<index-div>
+   			<index-title-group>
+    			<title>N</title>
+   			</index-title-group>
+   			<p>Content of index div</p>
+   			<index-entry>
+    			<term>Navy</term>
+    			<x>.</x>
+    			<see-entry>Armed forces</see-entry>
+    			<x>.</x>
+   			</index-entry>
+   			<index-entry>
+    			<term>Necessary and proper clause, congressional power</term>
+   			</index-entry>
+   			<index-entry>
+    			<term>Newsgathering as commerce</term>
+   			</index-entry>
+  		</index-div>
+	</index>
+</index-group>
+^D
+[ Header
+    1 ( "" , [] , [] ) [ Str "Index" , Space , Str "group" ]
+, Para
+    [ Str "Content"
+    , Space
+    , Str "of"
+    , Space
+    , Str "index"
+    , Space
+    , Str "group"
+    ]
+, Header 2 ( "" , [] , [] ) [ Str "Index" ]
+, Para
+    [ Str "Content" , Space , Str "of" , Space , Str "index" ]
+, Header 3 ( "" , [] , [] ) [ Str "N" ]
+, Para
+    [ Str "Content"
+    , Space
+    , Str "of"
+    , Space
+    , Str "index"
+    , Space
+    , Str "div"
+    ]
+, Plain [ Str "Navy" ]
+, Plain [ Str "." ]
+, Plain [ Str "Armed" , Space , Str "forces" ]
+, Plain [ Str "." ]
+, Plain
+    [ Str "Necessary"
+    , Space
+    , Str "and"
+    , Space
+    , Str "proper"
+    , Space
+    , Str "clause,"
+    , Space
+    , Str "congressional"
+    , Space
+    , Str "power"
+    ]
+, Plain
+    [ Str "Newsgathering"
+    , Space
+    , Str "as"
+    , Space
+    , Str "commerce"
+    ]
+]
+```