chore: adapt theme to new template system (#696)

* Adapted theme's layout to [Hugo v0.146.0](https://gohugo.io/templates/new-templatesystem-overview/)
* Bumped minimal Hugo version to v0.146.0

layouts/_partials/components/codeblock.html

@@ -0,0 +1,29 @@
+{{ $filename := .filename | default "" -}}
+{{ $base_url := .base_url | default "" -}}
+{{ $lang := .lang | default "" }}
+{{ $content := .content }}
+{{ $options := .options | default (dict) }}
+
+{{- if $filename -}}
+  <div class="filename not-prose" dir="auto">
+    {{- if $base_url -}}
+
+      {{- $base_url = strings.TrimSuffix "/" $base_url -}}
+      {{- $filename = strings.TrimPrefix "/" $filename -}}
+      {{- $file_url := urls.JoinPath $base_url $filename -}}
+
+      <a class="hx:no-underline hx:inline-flex hx:items-center hx:gap-1" href="{{ $file_url }}" target="_blank" rel="noopener noreferrer">
+          <span>{{- $filename -}}</span>
+          {{- partial "utils/icon" (dict "name" "external-link" "attributes" "height=1em") -}}
+      </a>
+    {{- else -}}
+      {{- $filename -}}
+    {{- end -}}
+  </div>
+{{- end -}}
+
+{{- if transform.CanHighlight $lang -}}
+  <div>{{- highlight $content $lang $options -}}</div>
+{{- else -}}
+  <div><pre><code>{{ $content }}</code></pre></div>
+{{- end -}}