Switch to Hugo

This commit includes all the needed workarounds and most changes from the main branch for everything to work, like:

* removing empty lines in raw HTML that break output
* read .browserslistrc, CSS variables from disk instead of duplicating it
* using Hugo mounts
* using Hugo for the docs CSS/JS
* move ToC Sass code to a separate file while adapting it for Hugo

Thus, this patch makes our npm scripts faster since lint runs on one step and there's no separate docs assets processing.

site/layouts/shortcodes/callout.html

@@ -0,0 +1,10 @@
+{{- /*
+  Usage: `callout "type"`,
+  where type is one of info (default), danger, warning
+*/ -}}
+
+{{- $css_class := .Get 0 | default "info" -}}
+
+<div class="bd-callout bd-callout-{{ $css_class }}">
+{{ .Inner | markdownify }}
+</div>

site/layouts/shortcodes/docsref.html

@@ -0,0 +1 @@
+{{- relref . ((printf "docs/%s%s" $.Site.Params.docs_version (.Get 0)) | relURL) -}}

site/layouts/shortcodes/example.html

@@ -0,0 +1,26 @@
+{{- /*
+  Usage: `example [args]`
+
+  `args` are optional and can be one of the following:
+    id: the `div`'s id - default: ""
+    class: any extra class(es) to be added to the `div` - default ""
+    show_preview: if the preview should be output in the HTML - default: `true`
+    show_markup: if the markup should be output in the HTML - default: `true`
+*/ -}}
+
+{{- $lang := .Get "lang" | default "html" -}}
+{{- $show_preview := .Get "show_preview" | default true -}}
+{{- $show_markup := .Get "show_markup" | default true -}}
+{{- $input := .Inner -}}
+
+{{- if eq $show_preview true -}}
+<div{{ with .Get "id" }} id="{{ . }}"{{ end }} class="bd-example{{ with .Get "class" }} {{ . }}{{ end }}">
+  {{- $input -}}
+</div>
+{{- end -}}
+
+{{- if eq $show_markup true -}}
+  {{- $content := replaceRE `<svg class="bd\-placeholder\-img(?:\-lg)?(?: *?bd\-placeholder\-img\-lg)? ?(.*?)".*?<\/svg>\n` `<img src="..." class="$1" alt="...">` $input -}}
+  {{- $content = replaceRE ` (class=" *?")` "" $content -}}
+  {{- highlight (trim $content "\n") $lang "" -}}
+{{- end -}}

site/layouts/shortcodes/markdown.html

@@ -0,0 +1 @@
+{{- .Inner | markdownify -}}

site/layouts/shortcodes/param.html

@@ -0,0 +1,12 @@
+{{- /*
+  Work around wrong escapes in integrity attributes.
+*/ -}}
+
+{{- $name := .Get 0 -}}
+{{- with $name -}}
+{{- $value := $.Page.Param . -}}
+{{- if in $name "_hash" -}}
+  {{- $value = $value | safeHTML -}}
+{{- end -}}
+{{- with $value }}{{ . }}{{ else }}{{ errorf "Param %q not found: %s" $name $.Position }}{{ end -}}
+{{- else }}{{ errorf "Missing param key: %s" $.Position }}{{ end -}}

site/layouts/shortcodes/partial.html

@@ -0,0 +1 @@
+{{ partial (.Get 0) . }}

site/layouts/shortcodes/placeholder.html

@@ -0,0 +1,30 @@
+{{- /*
+  Usage: `placeholder args`
+
+  args can be one of the following:
+    title: Used in the SVG `title` tag, default "Placeholder"
+    text: The text to show in the image - default: "width x height"
+    class: default: "bd-placeholder-img"
+    color: The text color (foreground) - default: "#dee2e6"
+    background: The background color - default: "#868e96"
+    width: default: 100%
+    height: default: 180px
+*/ -}}
+
+{{- $grays := $.Site.Data.grays -}}
+{{- $title := .Get "title" | default "Placeholder" -}}
+{{- $class := .Get "class" -}}
+{{- $color := .Get "color" | default (index $grays 2).hex -}}
+{{- $background := .Get "background" | default (index $grays 5).hex -}}
+{{- $width := .Get "width" | default "100%" -}}
+{{- $height := .Get "height" | default "180" -}}
+{{- $text := .Get "text" | default (printf "%sx%s" $width $height) -}}
+
+{{- $show_title := not (eq $title "false") -}}
+{{- $show_text := not (eq $text "false") -}}
+
+<svg class="bd-placeholder-img{{ with $class }} {{ . }}{{ end }}" width="{{ $width }}" height="{{ $height }}" xmlns="http://www.w3.org/2000/svg"{{ if (or $show_title $show_text) }} role="img" aria-label="{{ if $show_title }}{{ $title }}{{ if $show_text }}: {{ end }}{{ end }}{{ if ($show_text) }}{{ $text }}{{ end }}"{{ else }} aria-hidden="true"{{ end }} preserveAspectRatio="xMidYMid slice" focusable="false">
+  {{- if $show_title -}}<title>{{ $title }}</title>{{- end -}}
+  <rect width="100%" height="100%" fill="{{ $background }}"/>
+  {{- if $show_text -}}<text x="50%" y="50%" fill="{{ $color }}" dy=".3em">{{ $text }}</text>{{- end -}}
+</svg>

site/layouts/shortcodes/year.html

@@ -0,0 +1,5 @@
+{{- /*
+  Output the current year
+*/ -}}
+
+{{- now.Format "2006" -}}