bump md_exporter plugin to version 3.2.1

[bowenliang123]

Plugin Submission Form

1. Metadata

• Author: bowenliang123
• Github Repository:

2. Submission Type

• New plugin submission
• Version update for existing plugin

3. Description

• fix image links not found on Marketplace , by moving doc's screenshots from assets/ back to _assets/

4. Checklist

• I have read and followed the Publish to Dify Marketplace guidelines
• I have read and comply with the Plugin Developer Agreement
• I confirm my plugin works properly on both Dify Community Edition and Cloud Version
• I confirm my plugin has been thoroughly tested for completeness and functionality
• My plugin brings new value to Dify

5. Documentation Checklist

Please confirm that your plugin README includes all necessary information:

• Step-by-step setup instructions
• Detailed usage instructions
• All required APIs and credentials are clearly listed
• Connection requirements and configuration details
• Link to the repository for the plugin source code

6. Privacy Protection Information

Based on Dify Plugin Privacy Protection Guidelines:

Data Collection

Privacy Policy

• I confirm that I have prepared and included a privacy policy in my plugin package based on the Plugin Privacy Protection Guidelines