fix: dict type page parameters fall back to site parameters using merge behavior (#670)

> The `Param` method on a `Page` object looks for the given `KEY` in page parameters, and returns the corresponding value. If it cannot find the `KEY `in page parameters, it looks for the `KEY` in site parameters. If it cannot find the `KEY` in either location, the Param method returns `nil`.
>
> See: https://gohugo.io/methods/page/param/

So `.Page.Param` is only suitable for simple types.

layouts/_markup/render-codeblock-json.html

@@ -1,4 +1,4 @@
-{{- $jsonViewer := .Attributes | merge (.Page.Param "jsonViewer") -}}
+{{- $jsonViewer := .Attributes | merge .Page.Params.jsonViewer | merge .Page.Site.Params.jsonViewer -}}
 {{- if $jsonViewer.enable -}}
   {{- $attrs := printf `expand-depth="%v"` $jsonViewer.expanddepth -}}
   {{- $copyable := false -}}