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/marker.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="M408.8 0c-27.4 0-53.6 10.9-73 30.2L318.1 48 305 34.9c-28.1-28.1-73.7-28.1-101.8 0L103 135c-9.4 9.4-9.4 24.6 0 33.9s24.6 9.4 33.9 0L237.1 68.9c9.4-9.4 24.6-9.4 33.9 0L284.1 81.9 184 182.1 329.9 328 481.8 176.2c19.4-19.4 30.2-45.6 30.2-73 0-57-46.2-103.2-103.2-103.2zM102.4 263.7c-49.9 49.9-83.3 114-95.5 183.5L.4 483.8C-1 491.6 1.5 499.4 7 505s13.4 8 21.1 6.7l36.7-6.5c69.5-12.3 133.6-45.6 183.5-95.5L296 361.9 150.1 216 102.4 263.7z"/></svg>