DOC: Add links to previous versions in the Doxygen footer

To be updated with each minor release.

Documentation/Doxygen/DoxygenFooter.html

@@ -13,12 +13,19 @@
 <!--BEGIN !GENERATE_TREEVIEW-->
 <hr class="footer"/>
 <div class="footer" align="left">
-  <small>Tarballs of the nightly generated Doxygen documentation are available
+  <p><small>Tarballs of the nightly generated Doxygen documentation are available
     for the
     <a href="https://itk.org/files/NightlyDoxygen/InsightDoxygenDocHtml.tar.gz">html</a>,
     <a href="https://itk.org/files/NightlyDoxygen/InsightDoxygenDocXml.tar.gz">xml</a>, and
     <a href="https://itk.org/files/NightlyDoxygen/InsightDoxygenDocTag.gz">tag file</a>.
-  </small>
+  </small></p>
+  <p><small>Previous versions of this documentation for version:
+    <a href="https://itk.org/Doxygen52/html/index.html">5.2</a>,
+    <a href="https://itk.org/Doxygen51/html/index.html">5.1</a>,
+    <a href="https://itk.org/Doxygen50/html/index.html">5.0</a>,
+    <a href="https://itk.org/Doxygen413/html/index.html">4.13</a>,
+    <a href="https://itk.org/Doxygen320/html/index.html">3.20</a>.
+  </small></p>
 </div>
 <address class="footer"><small>
 Generated on <span id="datetime">unknown</span> for $projectname by &#160;