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/amazon.svg

@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 448 512"><!--! 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="M257.7 162.7c-48.7 1.8-169.5 15.5-169.5 117.5 0 109.5 138.3 114 183.5 43.2 6.5 10.2 35.4 37.5 45.3 46.8l56.8-56s-32.3-25.3-32.3-52.8l0-147.1C341.5 89 317 32 229.2 32 141.2 32 94.5 87 94.5 136.3l73.5 6.8c16.3-49.5 54.2-49.5 54.2-49.5 40.7-.1 35.5 29.8 35.5 69.1zm0 86.8c0 80-84.2 68-84.2 17.2 0-47.2 50.5-56.7 84.2-57.8l0 40.6zM393.7 413c-7.7 10-70 67-174.5 67S34.7 408.5 10.2 379c-6.8-7.7 1-11.3 5.5-8.3 73.3 44.5 187.8 117.8 372.5 30.3 7.5-3.7 13.3 2 5.5 12zm39.8 2.2c-6.5 15.8-16 26.8-21.2 31-5.5 4.5-9.5 2.7-6.5-3.8s19.3-46.5 12.7-55c-6.5-8.3-37-4.3-48-3.2-10.8 1-13 2-14-.3-2.3-5.7 21.7-15.5 37.5-17.5 15.7-1.8 41-.8 46 5.7 3.7 5.1 0 27.1-6.5 43.1z"/></svg>