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/_partials/home_info.html

@@ -0,0 +1,14 @@
+{{- with site.Params.homeInfoParams }}
+<article class="first-entry home-info">
+    <header class="entry-header">
+        <h1>{{ .Title | markdownify }}</h1>
+    </header>
+    <div class="entry-content md-content">
+        {{ $opts := dict "display" "block" }}
+        {{ .Content | $.Page.RenderString $opts }}
+    </div>
+    <footer class="entry-footer">
+        {{ partial "social_icons.html" (dict "align" site.Params.homeInfoParams.AlignSocialIconsTo) }}
+    </footer>
+</article>
+{{- end -}}