Add org mode to digital notebooks section

Add org-mode as it is a great TODO and note-taking tool.

index.html

@@ -2476,6 +2476,9 @@
 		<ul>
 			<li><a href="http://paperwork.rocks/">Paperwork</a> - Open source and self-hosted solution. For PHP / MySQL servers.</li>
 		</ul>
+		<ul>
+                        <li><a href="https://orgmode.org">Org mode</a> - A major mode for GNU Emacs. Org mode is for keeping notes, maintaining TODO lists, planning projects, and authoring documents with a fast and effective plain-text system. </li>
+                </ul>
 
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