40C3: tours, schedule data, tour map and calendar entries

- tour-map shortcode: Leaflet map of the tour locations with routes from the
  Congress, from the map/tours sections of data/schedule/<event>.yaml; Leaflet
  and the OSMIC, Maki and Temaki icon sets vendored; 39C3 uMap data converted.
- calendar shortcode: per tour date, a pill with an .ics download (iCalendar)
  and a Google Calendar link; Font Awesome Free vendored, fa-icon partial.
- README sections for the calendar and tour map shortcodes and the map data.

assets/vendor/icons/maki/art-gallery.svg

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<svg height="15" viewBox="0 0 15 15" width="15" xmlns="http://www.w3.org/2000/svg" id="art-gallery">
+  <path d="m10.71 3-2.86-2.849996c-.1945-.1960996-.511-.1973996-.7071-.0029-.001.001-.0019.0019-.0029.0029l-2.85 2.849996h-2.79c-.2761 0-.5.2239-.5.5v9c0 .2761.2239.5.5.5h12c.2761 0 .5-.2239.5-.5v-9c0-.2761-.2239-.5-.5-.5zm-3.21-1.79 1.79 1.79h-3.58zm5.5 10.79h-11v-8h11zm-8-5c-.5523 0-1-.4477-1-1s.4477-1 1-1 1 .4477 1 1-.4477 1-1 1zm7 4h-7.5l1.5-3 1.25 2.5 2.25-4.5z"/>
+</svg>