doctoc: fix

CONTRIBUTING.md

@@ -2,6 +2,14 @@
 
 Thank you for your interest in making a contribution to metsrw.
 
+<!-- START doctoc generated TOC please keep comment here to allow auto update -->
+<!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->
+**Table of Contents**  *generated with [DocToc](https://github.com/thlorenz/doctoc)*
+
+- [Design & API](#design--api)
+
+<!-- END doctoc generated TOC please keep comment here to allow auto update -->
+
 Since this project is used mostly in the general context of Archivematica, we
 invite you to read the [Archivematica contributing guide](https://github.com/artefactual/archivematica/blob/qa/1.x/CONTRIBUTING.md)
 to learn how to contribute to metsrw.
@@ -13,6 +21,7 @@ below.
 
 ## Design & API
 
-To provide feedback on the design and the API of metsrw, please refer yourself to the [metsrw wiki].
+To provide feedback on the design and the API of metsrw, please refer yourself
+to the [metsrw wiki].
 
-[metsrw wiki]: https://github.com/artefactual-labs/mets-reader-writer/wiki
+[metsrw wiki]: https://github.com/artefactual-labs/mets-reader-writer/wiki