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/square-check.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="M384 32c35.3 0 64 28.7 64 64l0 320c0 35.3-28.7 64-64 64L64 480c-35.3 0-64-28.7-64-64L0 96C0 60.7 28.7 32 64 32l320 0zM342 145.7c-10.7-7.8-25.7-5.4-33.5 5.3L189.1 315.2 137 263.1c-9.4-9.4-24.6-9.4-33.9 0s-9.4 24.6 0 33.9l72 72c5 5 11.9 7.5 18.8 7s13.4-4.1 17.5-9.8L347.3 179.2c7.8-10.7 5.4-25.7-5.3-33.5z"/></svg>