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/chess-bishop.svg

@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 320 512"><!--! 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 384L48.3 368.3C17.4 337.4 0 295.4 0 251.7 0 213.1 13.5 175.8 38.2 146.1L106.7 64 96 64C78.3 64 64 49.7 64 32S78.3 0 96 0L224 0c17.7 0 32 14.3 32 32s-14.3 32-32 32l-10.7 0 47.6 57.1-85.9 85.9c-9.4 9.4-9.4 24.6 0 33.9s24.6 9.4 33.9 0l82.3-82.3c18.7 27.3 28.7 59.7 28.7 93 0 43.7-17.4 85.7-48.3 116.6L256 384 312.2 454.3c5 6.3 7.8 14.1 7.8 22.2 0 19.6-15.9 35.5-35.5 35.5L35.5 512c-19.6 0-35.5-15.9-35.5-35.5 0-8.1 2.7-15.9 7.8-22.2L64 384z"/></svg>