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/regular/file-powerpoint.svg

@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 384 512"><!--! 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="M64 48l112 0 0 88c0 39.8 32.2 72 72 72l88 0 0 240c0 8.8-7.2 16-16 16L64 464c-8.8 0-16-7.2-16-16L48 64c0-8.8 7.2-16 16-16zM224 67.9l92.1 92.1-68.1 0c-13.3 0-24-10.7-24-24l0-68.1zM64 0C28.7 0 0 28.7 0 64L0 448c0 35.3 28.7 64 64 64l256 0c35.3 0 64-28.7 64-64l0-261.5c0-17-6.7-33.3-18.7-45.3L242.7 18.7C230.7 6.7 214.5 0 197.5 0L64 0zm88 256c-13.3 0-24 10.7-24 24l0 128c0 13.3 10.7 24 24 24s24-10.7 24-24l0-16 28 0c37.6 0 68-30.4 68-68s-30.4-68-68-68l-52 0zm52 88l-28 0 0-40 28 0c11 0 20 9 20 20s-9 20-20 20z"/></svg>