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/solar-panel.svg

@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 576 512"><!--! 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="M121.8 32c-30 0-56 20.8-62.5 50.1L9.6 306.1C.7 346.1 31.1 384 72 384l184.1 0 0 64-64 0c-17.7 0-32 14.3-32 32s14.3 32 32 32l192 0c17.7 0 32-14.3 32-32s-14.3-32-32-32l-64 0 0-64 184.1 0c40.9 0 71.4-37.9 62.5-77.9l-49.8-224C510.4 52.8 484.5 32 454.5 32L121.8 32zM245.6 96l85.2 0 7.3 88-99.8 0 7.3-88zm-55.5 88l-87.8 0 19.6-88 75.6 0-7.3 88zM91.6 232l94.5 0-7.3 88-106.7 0 19.6-88zm142.6 0l107.8 0 7.3 88-122.5 0 7.3-88zm156 0l94.5 0 19.6 88-106.7 0-7.3-88zM474 184l-87.8 0-7.3-88 75.6 0 19.6 88z"/></svg>