Resolve "Custom slide presentation markdown is not converted to HTML"

What does this mr do?

markdown wasn't being rendered correctly.

Actions taken to fix bug

Steps are described in the issue desc #644 (closed)

Screenshots

Does this MR meet the acceptance criteria?

• I have added a changelog entry to reflect the significant changes I made and the bug I fixed.
• A test was created to test the bug.
• I have updated the documentation accordingly.
• I adhere to the style guide.

Closes #644 (closed)