Better link to Windows instructions

[stefanspringer1]

Is your feature request related to a problem? Please describe

The link “Instructions“ on https://www.swift.org/install/ points to https://www.swift.org/install/windows/#installation-via-windows-package-manager, and such the user might miss the introductory parts on that page, to first understand that Visual Studio (and Git) is needed, and one should not forget the developer mode. The user is somehow too much thrown into cold water (and might miss the developer mode).

Describe the solution you'd like

Point the link “Instructions“ on https://www.swift.org/install/ to https://www.swift.org/install/windows.

Describe alternatives you've considered

Give notice about the introductory parts in each installation type section. (This might be even better because it solves the same problem also for the additional install options.)

[federicobucchi]

@stefanspringer1 change has been merged