put quarto-html-before-body script really at top

we don't have complete control over where 'before body' really is, with so many
components contributing to the array via mergeConfigs

so use a postprocessor for this

Author: gordonwoodhull

src/format/html/format-html-bootstrap.ts

@@ -78,9 +78,7 @@ import {
   documentTitleScssLayer,
   processDocumentTitle,
 } from "./format-html-title.ts";
-import {
-  darkModeDefault,
-} from "./format-html-info.ts";
+import { darkModeDefault } from "./format-html-info.ts";
 
 import { kTemplatePartials } from "../../command/render/template.ts";
 import { isHtmlOutput } from "../../config/format.ts";
@@ -520,6 +518,14 @@ function bootstrapHtmlPostprocessor(
     );
     resources.push(...titleResourceFiles);
 
+    // put quarto-html-before-body script at top of body
+    const beforeBodyScript = doc.querySelector(
+      "script#quarto-html-before-body",
+    );
+    if (beforeBodyScript) {
+      doc.body.insertBefore(beforeBodyScript, doc.body.firstChild);
+    }
+
     // Process the elements of this document into an appendix
     if (
       format.metadata[kAppendixStyle] !== false &&