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/brands/erlang.svg

@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 640 512"><!--! 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="M87.2 53.5l-87.2 0 0 405 100.4 0c-49.7-52.6-78.8-125.3-78.7-212.1-.1-76.7 24-142.7 65.5-192.9zm238.2 9.7c-45.9 .1-85.1 33.5-89.2 83.2l169.9 0c-1.1-49.7-34.5-83.1-80.7-83.2zm230.7-9.6l.3 0-.1-.1-.2 .1zm.3 0c31.4 42.7 48.7 97.5 46.2 162.7 .5 6 .5 11.7 0 24.1l-372.4 0c-.2 109.7 38.9 194.9 138.6 195.3 68.5-.3 118-51 151.9-106.1l96.4 48.2c-17.4 30.9-36.5 57.8-57.9 80.8l80.8 0 0-405-83.6 0z"/></svg>