fix to CVE-2021-29024 #735

[naui95]

Pull Request Checklist

• My code follows the code formatting guidelines.
• I have an issue ID for this pull request. (CVE-2021-29024: Misconfigured webserver, unauthenticated directory listing #735 )
• I selected the corresponding branch.
• I have rebased my changes on top of the corresponding branch.

Issue Type (Please check one or more)

• Bugfix
• Improvement of an existing Feature
• New Feature

I couldn't figure out how are you working with the branches, so i targeted the develop branch that seems to be the only active one.
The index.html files in the folders prevent a poorly configured server from allowing browsers to list the content of the folder. I hope the contribution is ok.