Allow a body heading alongside the front matter title in the markdown linter config

Set MD025 front_matter_title to an empty pattern so a front matter title:
is no longer counted as the document's top-level heading. Pages can now
carry both the front matter title MkDocs uses for navigation and the body
heading that renders on github.com.

An empty pattern is used rather than disabling MD025, so the rule still
reports a genuinely duplicated top-level heading. Converges with the same
setting in MSXOrg/docs.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Author: MariusStorhaug

.github/linters/.markdown-lint.yml

@@ -14,6 +14,8 @@ MD007:
 MD013:
   line_length: 808 # Line length
 MD024: false # no-duplicate-heading, INPUTS and OUTPUTS _can_ be the same item
+MD025:
+  front_matter_title: '' # Allow a body H1 alongside the front matter title
 MD026:
   punctuation: '.,;:!。，；:' # List of not allowed
 MD029: false # Ordered list item prefix