markdownlint: replace MD033 global disable with element allowlist (#422)

* Initial plan

* fix: whitelist specific HTML elements for MD033 instead of disabling globally

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Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: jbampton <418747+jbampton@users.noreply.github.com>

Author: Copilot

.github/linters/.markdown-lint.yml

@@ -10,7 +10,8 @@ MD024: false
 MD051: false
 
 # MD033/no-inline-html Inline HTML
-MD033: false
+MD033:
+  allowed_elements: ["div", "h1"]
 
 # MD036/no-emphasis-as-heading Emphasis used instead of a heading
 MD036: false