Sage-Windows: new released based on SageMath 8.4 and installer 0.4.1

[Samuel Lelièvre]

Following the recent release of SageMath 8.4,
the Sage-Windows installer is available.

Visit the Windows download page on the SageMath website:

http://www.sagemath.org/download-windows.html

and from there,
- either use the link to GitHub and download from there,
- or download from your nearest download mirror.

In either case you should obtain an executable called

SageMath-8.4-Installer-v0.4.1.exe

which you can double-click to start the installer.