fix(utils): parse Markdown headings with CRLF line break (#7043)

packages/docusaurus-utils/src/__tests__/markdownUtils.test.ts

@@ -253,6 +253,22 @@ Lorem Ipsum
     });
   });
 
+  it('parses markdown h1 title with CRLF break', () => {
+    const markdown = `# Markdown Title\r\n\r\nLorem Ipsum`;
+    expect(parseMarkdownContentTitle(markdown)).toEqual({
+      content: markdown,
+      contentTitle: 'Markdown Title',
+    });
+  });
+
+  it('parses markdown h1 setext title with CRLF break', () => {
+    const markdown = `Markdown Title\r\n=====\r\n\r\nLorem Ipsum`;
+    expect(parseMarkdownContentTitle(markdown)).toEqual({
+      content: markdown,
+      contentTitle: 'Markdown Title',
+    });
+  });
+
   it('parses markdown h1 title at the top (atx style with closing #)', () => {
     const markdown = dedent`
 

packages/docusaurus-utils/src/markdownUtils.ts

@@ -198,13 +198,13 @@ export function parseMarkdownContentTitle(
   // `import` nodes, as broken syntax can't render anyways. That means any block
   // that has `import` at the very beginning and surrounded by empty lines.
   const contentWithoutImport = content
-    .replace(/^(?:import\s(?:.|\n(?!\n))*\n{2,})*/, '')
+    .replace(/^(?:import\s(?:.|\r?\n(?!\r?\n))*(?:\r?\n){2,})*/, '')
     .trim();
 
-  const regularTitleMatch = /^#[ \t]+(?<title>[^ \t].*)(?:\n|$)/.exec(
+  const regularTitleMatch = /^#[ \t]+(?<title>[^ \t].*)(?:\r?\n|$)/.exec(
     contentWithoutImport,
   );
-  const alternateTitleMatch = /^(?<title>.*)\n=+(?:\n|$)/.exec(
+  const alternateTitleMatch = /^(?<title>.*)\r?\n=+(?:\r?\n|$)/.exec(
     contentWithoutImport,
   );