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/bitbucket.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="M22.2 32c-2.1 0-4.2 .4-6.1 1.1s-3.7 1.9-5.2 3.4-2.7 3.2-3.5 5.1-1.3 4-1.3 6.1c0 .9 .1 1.9 .2 2.8L74.1 462.7c.8 5.1 3.4 9.7 7.3 13s8.8 5.2 14 5.2l325.7 0c3.8 .1 7.5-1.3 10.5-3.7s4.9-5.9 5.5-9.7L505 50.7c.7-4.2-.3-8.4-2.8-11.9s-6.2-5.7-10.4-6.4c-.9-.1-1.9-.2-2.8-.2L22.2 32zM308.1 329.8l-104 0-28.1-147 157.3 0-25.2 147z"/></svg>