href are escaped by Pandoc 3.2.1 breaking toc

[cderv]

This (edit: #1776) just became very relevant for me. It turns out, pandoc started to escape href URIs starting with 3.2.1 because of https://github.com/jgm/pandoc/issues/9905

This specifically broke all toc entries in my document that do not consisted solely of ascii characters:

Uncaught Error: Syntax error, unrecognized expression: #bundesl%C3%A4nder
    jQuery 7
    refresh file:///XX/report_files/bootstrap-3.3.7/js/bootstrap.min.js:6
    jQuery 3
    refresh file:///XX/report_files/bootstrap-3.3.7/js/bootstrap.min.js:6
    b file:///XX/report_files/bootstrap-3.3.7/js/bootstrap.min.js:6
    c file:///XX/report_files/bootstrap-3.3.7/js/bootstrap.min.js:6
    jQuery 2
    c file:///XX/report_files/bootstrap-3.3.7/js/bootstrap.min.js:6
    <anonymous> file:///XX/report_files/downcute-0.1/downcute.js:44
    EventListener.handleEvent* file:///XX/report_files/downcute-0.1/downcute.js:11

A way to tell pandoc to use --to html5 would solve this.

Originally posted by @octomike in https://github.com/rstudio/rmarkdown/issues/1776#issuecomment-2448533830