fix: Prevent extra blank lines on list items

src/serializers/markdown/plugins/paragraph.ts

@@ -3,7 +3,8 @@ import type Turndown from 'turndown'
 
 /**
  * A Turndown plugin which adds a custom rule for paragraphs. This custom rule is required to avoid
- * adding unnecessary blank lines between paragraphs to plain-text documents.
+ * adding unnecessary blank lines between paragraphs to plain-text documents, and to list items in
+ * rich-text documents.
  *
  * @param nodeType The node object that matches this rule.
  * @param isPlainText Specifies if the schema represents a plain-text document.
@@ -12,8 +13,14 @@ function paragraph(nodeType: NodeType, isPlainText: boolean): Turndown.Plugin {
     return (turndown: Turndown) => {
         turndown.addRule(nodeType.name, {
             filter: 'p',
-            replacement(content) {
-                return isPlainText ? `\n${content}\n` : `\n\n${content}\n\n`
+            replacement(content, node) {
+                const useSingleLineSpacing =
+                    isPlainText ||
+                    // Paragraphs within list items should be wrapped with a single line feed to
+                    // maintain proper list formatting in rich-text documents.
+                    (!isPlainText && node.parentNode?.nodeName === 'LI')
+
+                return useSingleLineSpacing ? `\n${content}\n` : `\n\n${content}\n\n`
             },
         })
     }