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/linkedin-in.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="M100.3 448l-92.9 0 0-299.1 92.9 0 0 299.1zM53.8 108.1C24.1 108.1 0 83.5 0 53.8 0 39.5 5.7 25.9 15.8 15.8s23.8-15.8 38-15.8 27.9 5.7 38 15.8 15.8 23.8 15.8 38c0 29.7-24.1 54.3-53.8 54.3zM447.9 448l-92.7 0 0-145.6c0-34.7-.7-79.2-48.3-79.2-48.3 0-55.7 37.7-55.7 76.7l0 148.1-92.8 0 0-299.1 89.1 0 0 40.8 1.3 0c12.4-23.5 42.7-48.3 87.9-48.3 94 0 111.3 61.9 111.3 142.3l0 164.3-.1 0z"/></svg>