Implement new template system added with Hugo v0.146.0 (#1858)

* feat(layouts): move all files in layouts/_default up to the layouts/ root.

* feat(layouts): rename layouts/partials folder to layouts/_partials

* feat(layouts): rename layouts/shortcodes folder to layouts/_shortcodes

* feat(taxonomy): add new taxonomy layout template

A template named taxonomy.html used to be a candidate for both Page kind term and taxonomy, now it’s only considered for taxonomy.

layouts/_shortcodes/inTextImg.html

@@ -0,0 +1,5 @@
+{{- $Img := (.Get "url") }}
+{{- $height := (.Get "height") }}
+{{- $alt := (.Get "alt") }}
+
+<img class="in-text" height="{{ $height | default `15` }}" src="{{$Img}}" alt="{{$alt}}">