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/shoe-prints.svg

@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 576 512"><!--! 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="M296 192c-21.1-12.1-42.3-24.2-72-29.3l0-140.3C257.7 13 311.4 0 352 0 448 0 576 48 576 128s-119.6 96-176 96c-48 0-76-16-104-32zM128 32l48 0 0 128-48 0c-35.3 0-64-28.7-64-64s28.7-64 64-64zM232 320c28-16 56-32 104-32 56.4 0 176 16 176 96S384 512 288 512c-40.5 0-94.3-13-128-22.4l0-140.3c29.7-5.2 50.9-17.3 72-29.4zM64 480c-35.3 0-64-28.7-64-64s28.7-64 64-64l48 0 0 128-48 0z"/></svg>