text: Title: ✨Export to markdown and HTML
  Body: ## Feature Proposal
  
  We can easily export the document to markdown or html.
  
  We could add 2 buttons, "Copy to markdown" and "Copy to html" that will copy the editor in your clipboard to paste it where you want.
  
  See: https://www.blocknotejs.org/docs/editor-api/converting-blocks
  
  ![image](https://github.com/user-attachments/assets/a4f1c33b-3c43-4170-9ba3-a2b314f31872)
  
  ## Dropdown code location
  
  https://github.com/numerique-gouv/impress/blob/39d0211593511dd1030264f9a7e37e57cab1bce8/src/frontend/apps/impress/src/features/docs/doc-header/components/DocToolBox.tsx#L67-L130
  