OpenDocument/ODT writer: Added support for table of contents.

Closes #2836.

Thanks to @anayrat.

MANUAL.txt

@@ -1228,7 +1228,8 @@ as the following:
 :   non-null value if `--toc/--table-of-contents` was specified
 
 `toc-title`
-:   title of table of contents (works only with EPUB and docx)
+:   title of table of contents (works only with EPUB,
+    opendocument, odt, docx)
 
 `include-before`
 :   contents specified by `-B/--include-before-body` (may have

src/Text/Pandoc/Writers/OpenDocument.hs

@@ -220,6 +220,7 @@ writeOpenDocument opts (Pandoc meta blocks) = do
   let listStyles  = map listStyle (stListStyles s)
   let automaticStyles = vcat $ reverse $ styles ++ listStyles
   let context = defField "body" body
+              $ defField "toc" (writerTableOfContents opts)
               $ defField "automatic-styles" (render' automaticStyles)
               $ metadata
   case writerTemplate opts of