fix(save-post): update post.isMarkdown accordingly (#109)

Author: laggage

src/commands/posts-list/save-post.ts

@@ -149,6 +149,7 @@ export const savePostToCnblogs = async (input: Post | PostTreeItem | PostEditDto
     await saveFilePendingChanges(localFilePath);
     post.postBody = (await workspace.fs.readFile(Uri.file(localFilePath))).toString();
     post.title = await PostTitleSanitizer.unSanitize(post);
+    post.isMarkdown = path.extname(localFilePath).endsWith('md') || post.isMarkdown;
 
     if (!validatePost(post)) return false;