fix multi-paragraph blockquotes (markdoc#322)

Closes markdoc#321

Author: mfix-stripe

src/formatter.test.ts

@@ -693,4 +693,19 @@ ${'`'.repeat(4)}
 
     stable(source);
   });
+  it('multi-paragraph blockquotes', () => {
+    const source = `
+> Blockquote {% .class %}
+>
+> with two paragraphs`;
+
+    const expected = `
+> Blockquote {% .class %}
+> 
+> with two paragraphs
+`;
+
+    check(source, expected);
+    stable(expected);
+  });
 });

src/formatter.ts

@@ -215,10 +215,11 @@ function* formatNode(n: Node, o: Options = {}) {
       break;
     }
     case 'blockquote': {
-      yield NL;
-      yield indent;
-      yield '> ';
-      yield* trimStart(formatChildren(n, no));
+      const prefix = '>' + SPACE;
+      yield n.children
+        .map((child) => format(child, no).trimStart())
+        .map((d) => NL + indent + prefix + d)
+        .join(indent + prefix);
       break;
     }
     case 'hr': {