Pass .RenderShortcodes' Page to render hooks as .PageInner

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

markup/goldmark/render_hooks.go

@@ -49,6 +49,7 @@ func newLinks(cfg goldmark_config.Config) goldmark.Extender {
 
 type linkContext struct {
 	page        any
+	pageInner   any
 	destination string
 	title       string
 	text        hstring.RenderedString
@@ -64,6 +65,10 @@ func (ctx linkContext) Page() any {
 	return ctx.page
 }
 
+func (ctx linkContext) PageInner() any {
+	return ctx.pageInner
+}
+
 func (ctx linkContext) Text() hstring.RenderedString {
 	return ctx.text
 }
@@ -92,6 +97,7 @@ func (ctx imageLinkContext) Ordinal() int {
 
 type headingContext struct {
 	page      any
+	pageInner any
 	level     int
 	anchor    string
 	text      hstring.RenderedString
@@ -103,6 +109,10 @@ func (ctx headingContext) Page() any {
 	return ctx.page
 }
 
+func (ctx headingContext) PageInner() any {
+	return ctx.pageInner
+}
+
 func (ctx headingContext) Level() int {
 	return ctx.level
 }
@@ -186,6 +196,7 @@ func (r *hookedRenderer) renderImage(w util.BufWriter, source []byte, node ast.N
 		imageLinkContext{
 			linkContext: linkContext{
 				page:             ctx.DocumentContext().Document,
+				pageInner:        r.getPageInner(ctx),
 				destination:      string(n.Destination),
 				title:            string(n.Title),
 				text:             hstring.RenderedString(text),
@@ -200,6 +211,18 @@ func (r *hookedRenderer) renderImage(w util.BufWriter, source []byte, node ast.N
 	return ast.WalkContinue, err
 }
 
+func (r *hookedRenderer) getPageInner(rctx *render.Context) any {
+	pid := rctx.PeekPid()
+	if pid > 0 {
+		if lookup := rctx.DocumentContext().DocumentLookup; lookup != nil {
+			if v := rctx.DocumentContext().DocumentLookup(pid); v != nil {
+				return v
+			}
+		}
+	}
+	return rctx.DocumentContext().Document
+}
+
 func (r *hookedRenderer) filterInternalAttributes(attrs []ast.Attribute) []ast.Attribute {
 	n := 0
 	for _, x := range attrs {
@@ -274,6 +297,7 @@ func (r *hookedRenderer) renderLink(w util.BufWriter, source []byte, node ast.No
 		w,
 		linkContext{
 			page:             ctx.DocumentContext().Document,
+			pageInner:        r.getPageInner(ctx),
 			destination:      string(n.Destination),
 			title:            string(n.Title),
 			text:             hstring.RenderedString(text),
@@ -339,6 +363,7 @@ func (r *hookedRenderer) renderAutoLink(w util.BufWriter, source []byte, node as
 		w,
 		linkContext{
 			page:             ctx.DocumentContext().Document,
+			pageInner:        r.getPageInner(ctx),
 			destination:      url,
 			text:             hstring.RenderedString(label),
 			plainText:        label,
@@ -423,6 +448,7 @@ func (r *hookedRenderer) renderHeading(w util.BufWriter, source []byte, node ast
 		w,
 		headingContext{
 			page:             ctx.DocumentContext().Document,
+			pageInner:        r.getPageInner(ctx),
 			level:            n.Level,
 			anchor:           string(anchor),
 			text:             hstring.RenderedString(text),