How to keep Visual Studio from removing .md files from project?

I have one “.md” file which contains my changelog.

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Visual Studio keeps “removing” it from the project, such that it no longer shows up in “Go to all” lookup. I keep needing to right-click on it, and choose “Include in Project”. This fixes it for maybe a couple of days, but before long it gets unincluded again.

Is there any way to keep VS from doing this? I prefer to keep this file .md as opposed to .txt (though .txt doesn’t suffer from this problem), if possible.

I would rather suspect Unity. I think when it regenerates the project it does not include any files which is not recognized by it. But this is just a gut feeling, it is probable that I’m wrong.