Pdf to markdown (#2730)

# Description

Please provide a summary of the changes, including relevant motivation
and context.

Closes #(issue_number)

## Checklist

- [ ] I have read the [Contribution
Guidelines](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/CONTRIBUTING.md)
- [ ] I have performed a self-review of my own code
- [ ] I have attached images of the change if it is UI based
- [ ] I have commented my code, particularly in hard-to-understand areas
- [ ] If my code has heavily changed functionality I have updated
relevant docs on [Stirling-PDFs doc
repo](https://github.com/Stirling-Tools/Stirling-Tools.github.io/blob/main/docs/)
- [ ] My changes generate no new warnings
- [ ] I have read the section [Add New Translation
Tags](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/HowToAddNewLanguage.md#add-new-translation-tags)
(for new translation tags only)

---------

Co-authored-by: a <a>

cucumber/features/external.feature

@@ -204,4 +204,12 @@ Feature: API Validation
   Then the response status code should be 200
   And the response file should have size greater than 100
   And the response file should have extension ".pdf"
+  
+  Scenario: Convert PDF to Markdown format
+  Given I generate a PDF file as "fileInput"
+  And the pdf contains 3 pages with random text
+  When I send the API request to the endpoint "/api/v1/convert/pdf/markdown"
+  Then the response status code should be 200
+  And the response file should have size greater than 100
+  And the response file should have extension ".md"