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/fontawesome/solid/tower-observation.svg

@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 448 512"><!--! Font Awesome Free 7.3.1 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2026 Fonticons, Inc. --><path fill="currentColor" d="M209.7 3.4c9-4.5 19.6-4.5 28.6 0l160 80c15.8 7.9 22.2 27.1 14.3 42.9-5.6 11.2-16.9 17.7-28.6 17.7l0 80c0 17.7-14.3 32-32 32l-13 0 32 192 45 0c17.7 0 32 14.3 32 32s-14.3 32-32 32L32 512c-17.7 0-32-14.3-32-32s14.3-32 32-32l45 0 32-192-13 0c-17.7 0-32-14.3-32-32l0-80c-11.7 0-23-6.5-28.6-17.7-7.9-15.8-1.5-35 14.3-42.9l160-80zM310.7 448l-86.7-61.9-86.7 61.9 173.4 0zm-153-192l-3.5 21.2 69.9 49.9 69.9-49.9-3.5-21.2-132.7 0zm-12.3 73.9l-10.1 60.6 47.5-33.9-37.4-26.7zm119.9 26.7l47.5 33.9-10.1-60.6-37.4 26.7zM152 128c-13.3 0-24 10.7-24 24s10.7 24 24 24l144 0c13.3 0 24-10.7 24-24s-10.7-24-24-24l-144 0z"/></svg>