Hi
Based on my research, Microsoft does not have step by step documentation on how to implement this. Additionally, It seems that ftype and assoc are not powerful on systems running Windows 8 or later. Also ftype is not available from PowerShell. Refer - ftype
This is due to the fact that Microsoft decided in Windows 8 that users should be able to set default programs only via the built in GUI. This probably was due to security reasons and trouble with applications hijacking file type associations. Refer - https://blogs.windows.com/windows-insider/2015/05/20/announcing-windows-10-insider-preview-build-10122-for-pcs/