Issue with makrdown file path stored in post meta

As the complete path of markdown files to be imported gets stored in post meta. It causes an issue if:

1. The absolute path to the plugin folder then changes.
2. Name of the plugin changes.

Both of these issue happened in our case.

Had to run the following search-replace commands to fix this:

```bash
wp search-replace '/var/www/htdocs/wp-content/plugins/ee-markdown-importer/' '/var/www/htdocs/current/wp-content/plugins/wp-ee-docs-command/' --url=

wp search-replace '/var/www/htdocs/wp-content/plugins/wp-ee-docs-command/' '/var/www/htdocs/current/wp-content/plugins/wp-ee-docs-command/' --url=
```

首先追踪导入的 Markdown 文件路径是在何处写入 post meta 的；该 issue 没有提供文件名或测试名。在移动或重命名 plugin-directory 后重现该行为，然后验证已存储的引用无需使用文档中所述的 wp search-replace 命令仍然可用。

由索引模型根据 Issue 内容生成。