How to make sure that Markdown files are opened in Emacs (like normal files) and not in an external application?

Question

I have openwith installed in my Emacs. I use it to open spreadsheets, PDF, and other files in their respective external applications.

Recently I had an Org mode file with the following content:

 * [[file:c:/usr/dp/dev/misc/mentiflectax.com/content/posts/sometext.md][Text for the comment on Reddit]]

When I click on the link, a Windows dialog pops up "What application should this file be opened with?"

Since this is a Markdown file, I want it to be opened in Emacs like any other text file.

How can I achieve this, i. e. make sure that

• Markdown files are opened in Emacs and
• files of types configured via M-x customize-group RET openwith RET are still opened in the respective external applications?