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/brands/dolibarr.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="M167.6 160.2l0 319.5-119.4-1.3 0-446.4 155.6 0c68.2 0 121.7 17.2 160.3 51.7 45.9 41.2 68.8 97.1 68.8 167.8 0 67.6-19.6 122.7-58.8 165.5S285.3 480 223.6 480c-7.3 0-20.3-.2-36.6-.3l0-131.1 32.9-.2c69.6-.4 90.6-32.2 90.6-97 0-60.8-34.2-91.2-102.6-91.2l-40.3 0z"/></svg>