fix(markdown): ensure ending newline in import code

Author: meteorlxy

packages/@vuepress/markdown/__tests__/plugins/importCodePlugin.spec.ts

@@ -69,16 +69,16 @@ ${mdFixtureContent}\
 
       const expected = `\
 <pre><code class="language-js">\
-${jsFixtureContent.split('\n').slice(0, 2).join('\n')}\
+${jsFixtureContent.split('\n').slice(0, 2).join('\n').replace(/\n?$/, '\n')}\
 </code></pre>
 <pre><code class="language-js">\
-${jsFixtureContent.split('\n').slice(0).join('\n')}\
+${jsFixtureContent.split('\n').slice(0).join('\n').replace(/\n?$/, '\n')}\
 </code></pre>
 <pre><code class="language-md">\
-${mdFixtureContent.split('\n').slice(3, 5).join('\n')}\
+${mdFixtureContent.split('\n').slice(3, 5).join('\n').replace(/\n?$/, '\n')}\
 </code></pre>
 <pre><code class="language-md">\
-${mdFixtureContent.split('\n').slice(0, 5).join('\n')}\
+${mdFixtureContent.split('\n').slice(0, 5).join('\n').replace(/\n?$/, '\n')}\
 </code></pre>
 `
 

packages/@vuepress/markdown/src/plugins/importCodePlugin/resolveImportCode.ts

@@ -40,6 +40,7 @@ export const resolveImportCode = (
     importCode: fileContent
       .split('\n')
       .slice(lineStart ? lineStart - 1 : lineStart, lineEnd)
-      .join('\n'),
+      .join('\n')
+      .replace(/\n?$/, '\n'),
   }
 }