The main use case for this is to resolve links and resources (e.g. images) relative to the included `Page`.
A typical `include` would similar to this:
```handlebars
{{ with site.GetPage (.Get 0) }}
{{ .RenderShortcodes }}
{{ end }}
```
And when used in a Markdown file:
```markdown
{{% include "/posts/p1" %}}
```
Any render hook triggered while rendering `/posts/p1` will get `/posts/p1` when calling `.PageInner`.
Note that
* This is only relevant for shortcodes included with `{{%` that calls `.RenderShortcodes`.
* `.PageInner` is available in all render hooks that, before this commit, received `.Page`.
* `.PageInner` will fall back to the value of `.Page` if not relevant and will always have a value.
Fixes#12356
You can now create custom hook templates for code blocks, either one for all (`render-codeblock.html`) or for a given code language (e.g. `render-codeblock-go.html`).
We also used this new hook to add support for diagrams in Hugo:
* Goat (Go ASCII Tool) is built-in and enabled by default; just create a fenced code block with the language `goat` and start draw your Ascii diagrams.
* Another popular alternative for diagrams in Markdown, Mermaid (supported by GitHub), can also be implemented with a simple template. See the Hugo documentation for more information.
Updates #7765Closes#9538Fixes#9553Fixes#8520Fixes#6702Fixes#9558
