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/ruler-vertical.svg

@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 256 512"><!--! 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="M0 16C0-10.5 21.5-32 48-32l160 0c26.5 0 48 21.5 48 48l0 24-104 0c-13.3 0-24 10.7-24 24s10.7 24 24 24l104 0 0 48-72 0c-13.3 0-24 10.7-24 24s10.7 24 24 24l72 0 0 48-104 0c-13.3 0-24 10.7-24 24s10.7 24 24 24l104 0 0 48-72 0c-13.3 0-24 10.7-24 24s10.7 24 24 24l72 0 0 48-104 0c-13.3 0-24 10.7-24 24s10.7 24 24 24l104 0 0 24c0 26.5-21.5 48-48 48L48 544c-26.5 0-48-21.5-48-48L0 16z"/></svg>