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/h-square.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="M64 32C28.7 32 0 60.7 0 96L0 416c0 35.3 28.7 64 64 64l320 0c35.3 0 64-28.7 64-64l0-320c0-35.3-28.7-64-64-64L64 32zM320 168l0 176c0 13.3-10.7 24-24 24s-24-10.7-24-24l0-64-96 0 0 64c0 13.3-10.7 24-24 24s-24-10.7-24-24l0-176c0-13.3 10.7-24 24-24s24 10.7 24 24l0 64 96 0 0-64c0-13.3 10.7-24 24-24s24 10.7 24 24z"/></svg>