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.

layouts/_partials/fa-icon.html

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+{{- /*
+A Font Awesome icon as inline SVG, decorative (hidden from screen readers) and drawn in the
+current text colour. Param: the icon as "style/name", e.g. "regular/calendar-plus"; the files
+are in assets/vendor/fontawesome/. The SVG keeps its attribution comment (CC BY 4.0).
+*/ -}}
+{{- with resources.Get (printf "vendor/fontawesome/%s.svg" .) -}}
+  {{- replace .Content "<svg " `<svg class="fa-icon" aria-hidden="true" focusable="false" ` 1 | safeHTML -}}
+{{- else -}}
+  {{- errorf "fa-icon: no icon %q in assets/vendor/fontawesome/" . -}}
+{{- end -}}

layouts/_partials/ics-line.html

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+{{- /*
+One iCalendar (RFC 5545) content line: "NAME:value" plus CRLF, folded so that no line is
+longer than 75 bytes (continuation lines start with a space). Params: name, value, text
+(true to escape the value as TEXT: backslash, semicolon, comma and newlines).
+*/ -}}
+{{- $value := .value | default "" -}}
+{{- if .text -}}
+  {{- $value = $value | replaceRE `\\` `\\` | replaceRE `;` `\;` | replaceRE `,` `\,` | replaceRE `\r?\n` `\n` -}}
+{{- end -}}
+{{- $out := "" -}}
+{{- $line := "" -}}
+{{- $bytes := 0 -}}
+{{- range split (printf "%s:%s" .name $value) "" -}}
+  {{- if gt (add $bytes (len .)) 75 -}}
+    {{- $out = printf "%s%s\r\n " $out $line -}}
+    {{- $line = "" -}}
+    {{- $bytes = 1 -}}
+  {{- end -}}
+  {{- $line = printf "%s%s" $line . -}}
+  {{- $bytes = add $bytes (len .) -}}
+{{- end -}}
+{{- return printf "%s%s\r\n" $out $line -}}

layouts/_partials/tour-map-icon.html

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+{{- /*
+Returns a map icon as a data: URI, or "" if there is none by that name.
+The name is looked up in the vendored icon sets in assets/vendor/icons/, in the order
+osmic, maki, temaki; a prefix like "maki:garden" picks the set.
+*/ -}}
+{{- $name := . -}}
+{{- $sets := slice "osmic" "maki" "temaki" -}}
+{{- with findRESubmatch `^(osmic|maki|temaki):(.+)$` . 1 -}}
+  {{- $sets = slice (index . 0 1) -}}
+  {{- $name = index . 0 2 -}}
+{{- end -}}
+{{- $uri := "" -}}
+{{- range $sets -}}
+  {{- if not $uri -}}
+    {{- with resources.Get (printf "vendor/icons/%s/%s.svg" . $name) -}}
+      {{- $uri = printf "data:image/svg+xml;base64,%s" ((. | minify).Content | base64Encode) -}}
+    {{- end -}}
+  {{- end -}}
+{{- end -}}
+{{- return $uri -}}

layouts/_partials/tour-map-script.html

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+{{- /* Leaflet and the script for the tour-map shortcode, included by the base templates on pages that use it. */ -}}
+{{- with resources.Get "vendor/leaflet/leaflet.css" | fingerprint }}
+<link rel="stylesheet" href="{{ .RelPermalink }}" integrity="{{ .Data.Integrity }}" crossorigin="anonymous">
+{{- end }}
+{{- with resources.Get "vendor/leaflet/leaflet.js" | fingerprint }}
+<script src="{{ .RelPermalink }}" integrity="{{ .Data.Integrity }}" crossorigin="anonymous" defer></script>
+{{- end }}
+{{- with resources.Get "js/tour-map.js" | minify | fingerprint }}
+<script src="{{ .RelPermalink }}" integrity="{{ .Data.Integrity }}" crossorigin="anonymous" defer></script>
+{{- end }}