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/signs-post.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="M256.4 0c-17.7 0-32 14.3-32 32l0 32-160 0c-17.7 0-32 14.3-32 32l0 64c0 17.7 14.3 32 32 32l160 0 0 64-153.4 0c-4.2 0-8.3 1.7-11.3 4.7l-48 48c-6.2 6.2-6.2 16.4 0 22.6l48 48c3 3 7.1 4.7 11.3 4.7l153.4 0 0 96c0 17.7 14.3 32 32 32s32-14.3 32-32l0-96 160 0c17.7 0 32-14.3 32-32l0-64c0-17.7-14.3-32-32-32l-160 0 0-64 153.4 0c4.2 0 8.3-1.7 11.3-4.7l48-48c6.2-6.2 6.2-16.4 0-22.6l-48-48c-3-3-7.1-4.7-11.3-4.7l-153.4 0 0-32c0-17.7-14.3-32-32-32z"/></svg>