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/shapes.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 0c11.2 0 21.7 5.9 27.4 15.5l96 160c5.9 9.9 6.1 22.2 .4 32.2S363.5 224 352 224l-192 0c-11.5 0-22.2-6.2-27.8-16.2s-5.5-22.3 .4-32.2l96-160C234.3 5.9 244.8 0 256 0zM128 272a112 112 0 1 1 0 224 112 112 0 1 1 0-224zm200 16l112 0c22.1 0 40 17.9 40 40l0 112c0 22.1-17.9 40-40 40l-112 0c-22.1 0-40-17.9-40-40l0-112c0-22.1 17.9-40 40-40z"/></svg>