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/book-reader.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="M256 152a88 88 0 1 0 0-176 88 88 0 1 0 0 176zm0 298.7l0-149.3c16.3-6.8 32.9-13.7 49.7-20.7 39-16.2 80.8-24.6 123.1-24.6l19.2 0 0 160-19.2 0c-59.1 0-117.7 11.7-172.3 34.5l-.5 .2zM256 232l-25.1-10.5C184.1 202 133.9 192 83.2 192L48 192c-26.5 0-48 21.5-48 48L0 432c0 26.5 21.5 48 48 48l35.2 0c50.7 0 100.9 10 147.7 29.5l12.8 5.3c7.9 3.3 16.7 3.3 24.6 0l12.8-5.3c46.8-19.5 97-29.5 147.7-29.5l35.2 0c26.5 0 48-21.5 48-48l0-192c0-26.5-21.5-48-48-48l-35.2 0c-50.7 0-100.9 10-147.7 29.5L256 232z"/></svg>