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/droplet.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 512C86 512 0 426 0 320 0 228.8 130.2 45.9 166.6-3.5 172.5-11.5 181.8-16 191.8-16l.4 0c10 0 19.3 4.5 25.2 12.5 36.4 49.4 166.6 232.3 166.6 323.5 0 106-86 192-192 192zM112 312c0-13.3-10.7-24-24-24s-24 10.7-24 24c0 75.1 60.9 136 136 136 13.3 0 24-10.7 24-24s-10.7-24-24-24c-48.6 0-88-39.4-88-88z"/></svg>