Documentation for force-https.txt

How to use the force-https.txt?

We need to add information to the documentation

With #1087 it was introduced.

But `force-https.default.txt` is not anymore located in `/data`, now it is in root folder.

Start by reviewing the documentation around force-https.txt and the change introduced in issue #1087. Confirm the current location of force-https.default.txt in the repository root, then document how to use force-https.txt and its relationship to that file. Done means the documented usage and current path are accurate.

Written by the indexing model from the issue text.