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/regular/map.svg

@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 512 512"><!--! 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="M512 48c0-8.3-4.3-16-11.3-20.4s-15.9-4.8-23.3-1.1L352.5 88.1 180 29.4c-13.7-4.7-28.7-3.8-41.9 2.3L13.8 90.3C5.4 94.2 0 102.7 0 112L0 464c0 8.2 4.2 15.9 11.1 20.3s15.6 4.9 23.1 1.4l127.3-59.9 170.7 56.9c13.7 4.6 28.5 3.7 41.6-2.5l124.4-58.5c8.4-4 13.8-12.4 13.8-21.7l0-352zM144 82.1l0 299-96 45.2 0-299 96-45.2zm48 303.3l0-301.1 128 43.5 0 300.3-128-42.7zM368 134l96-47.4 0 298.2-96 45.2 0-296z"/></svg>