A new installer has been released that lets you put Windows 10 on ARM, which includes the Raspberry Pi. This installer is made by the same people who were able to put Windows 10 on the Lumia 950 and 950 XL.
On the Github page for the project developer Jose Manuel Nieto Sanchez says that the process is super easy to use and no hassle. You will however need a Raspberry Pi 3 Model B (or B+), MicroSD card (recommended with A1 rating), and a Windows 10 ARM64 Image (.wim).
Jose Manuel Nieto Sanchez also pointed out that the WoA Installer is only a tool with helps you with the deployment. WoA Installer needs a set of binaries, AKA the Core Package, to do its job. These binaries are not not mine and are bundled and offered just for convenience to make your life easier, since this tool is focused on simplicity.