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/chess-pawn.svg

@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 384 512"><!--! 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="M192-32c66.3 0 120 53.7 120 120 0 27-8.9 51.9-24 72 17.7 0 32 14.3 32 32s-14.3 32-32 32l-10.7 0 26.7 160 56.2 70.3c5 6.3 7.8 14.1 7.8 22.2 0 19.6-15.9 35.5-35.5 35.5L51.5 512c-19.6 0-35.5-15.9-35.5-35.5 0-8.1 2.7-15.9 7.8-22.2L80 384 106.7 224 96 224c-17.7 0-32-14.3-32-32s14.3-32 32-32c-15.1-20.1-24-45-24-72 0-66.3 53.7-120 120-120z"/></svg>