Adding a new feature to export themes as ZIP folders.

Author: thiagogq

settings.html

@@ -250,6 +250,7 @@
           <span>View and edit the &nbsp;&nbsp;<a id="open-rss-modal" class="button" href="#">RSS templates</a></span>
           <br/><br/>
           <span>Download a copy of the database in JSON format &nbsp;&nbsp;<button id="download-json-db" class="button">Download</button></span><br/><br/>
+          <span>Export current theme as a ZIP folder &nbsp;&nbsp;<button id="export-theme-zip" class="button">Export</button></span><br/><br/>
           <span>Grant permission to use persistent storage &nbsp;&nbsp;<button id="persistent-storage" class="button">Confirm</button></span><br/><br/>
           <span>Reset the Default Theme <span class="info-span" data-title="After importing the website database,&#010;you may need to update the Default Theme."><img src="images/info.svg"/></span>&nbsp;&nbsp;<button id="reset-default-theme" class="button">Reset</button></span><br/><br/>
           <br/>