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/mizuni.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 8a248 248 0 1 0 0 496 248 248 0 1 0 0-496zM176 359.9c-31.4 10.6-58.8 27.3-80 48.2L96 136c0-22.1 17.9-40 40-40s40 17.9 40 40l0 223.9zM296 350c-12.9-2-26.2-3.1-39.8-3.1-13.8 0-27.2 1.1-40.2 3.1l0-214c0-22.1 17.9-40 40-40s40 17.9 40 40l0 214zm120 57.7c-21.2-20.8-48.6-37.4-80-48L336 136c0-22.1 17.9-40 40-40s40 17.9 40 40l0 271.7z"/></svg>