feat: add hx- prefix to Hextra Tailwind CSS classes (#300)

* feat: add prefix to tailwind css classes

* fix: remove unnecessary prefixes

* fix: add missing prefix in other places

* chore: regenerate hugo_stats.json

* chore: run `npm run build:css`

* chore: add `hx-` prefix to _index.fa.md

* fix: lang switcher display issue

* fix: add `hx-` prefix to showcase/index.fa.md

* fix: lang switch param mistake

layouts/_default/_markup/render-heading.html

@@ -1,7 +1,7 @@
 <h{{ .Level }}>
   {{- .Text | safeHTML -}}
   {{- if gt .Level 1 -}}
-    <span class="absolute -mt-20" id="{{ .Anchor | safeURL }}"></span>
+    <span class="hx-absolute -hx-mt-20" id="{{ .Anchor | safeURL }}"></span>
     <a href="#{{ .Anchor | safeURL }}" class="subheading-anchor" aria-label="Permalink for this section"></a>
   {{- end -}}
 </h{{ .Level }}>