Bootstrap v5 Migration, Style Cleanups, Formular-Umgestaltung, Layout-Verbesserungen (schließt #222)

layouts/shortcodes/youtube.html

@@ -4,7 +4,7 @@
 {{- $id := .Get "id" | default (.Get 0) -}}
 {{- $class := .Get "class" | default (.Get 1) -}}
 {{- $title := .Get "title" | default "YouTube Video" }}
-<div {{ with $class }}class="{{ . }}"{{ else }}style="position: relative; padding-bottom: 56.25%; height: 0; overflow: hidden;"{{ end }}>
+<div {{ with $class }}class="{{ . }}" {{ else }} style="position: relative; padding-bottom: 56.25%; height: 0; overflow: hidden;"{{ end }}>
   <iframe src="https://{{ $ytHost }}/embed/{{ $id }}{{ with .Get "autoplay" }}{{ if eq . "true" }}?autoplay=1{{ end }}{{ end }}" {{ if not $class }}style="position: absolute; top: 0; left: 0; width: 100%; height: 100%; border:0;" {{ end }}allowfullscreen title="{{ $title }}"></iframe>
 </div>
 {{ end -}}