Move render hook examples to example dir to avoid Hugo warnings.

layouts/_markup/example-render-codeblock.html

@@ -1,15 +0,0 @@
-{{ .Page.Store.Set "codeblocks" true -}}
-{{ $result := transform.HighlightCodeBlock . -}}
-<div data-codeblock itemscope itemtype="https://schema.org/SoftwareSourceCode" {{ range $k, $v := .Attributes }}{{ printf " %s=%q" $k $v | safeHTMLAttr }}{{ end }}>
-<button data-codebutton class="codebutton" title="{{ i18n "copy_code" }}"><span>⧉</span></button>
-<meta itemprop="codeSampleType" content="snippet">
-<meta data-codetext itemprop="text" content="{{ .Inner | jsonify }}">
-{{ if .Type -}}
-<meta itemprop="programmingLanguage" content="{{ .Type }}">
-<pre tabindex="0" class="chroma">
-<code class="language-{{ .Type }}" data-lang="{{ .Type }}">{{ $result.Inner }}</code>
-</pre>
-{{ else -}}
-{{ $result.Wrapped }}
-{{ end -}}
-</div>