Convert docdock theme from submodule to native files and fix Hugo compatibility

themes/docdock/layouts/shortcodes/expand.html

@@ -0,0 +1,10 @@
+{{$expandMessage := T "Expand-title"}}
+<div class="expand">
+<div class="expand-label" style="cursor: pointer;" onclick="$h = $(this);$h.next('div').slideToggle(100,function () {$h.children('i').attr('class',function () {return $h.next('div').is(':visible') ? 'fa fa-chevron-down' : 'fa fa-chevron-right';});});">
+<i style="font-size:x-small;" class="fa fa-chevron-right"></i>
+<span>{{ if .IsNamedParams }}{{.Get "default" | default $expandMessage}}{{else}}{{.Get 0 | default $expandMessage}}{{end}}</span>
+</div>
+<div class="expand-content" style="display: none;">
+<p>{{.Inner | safeHTML }}</p>
+</div>
+</div>