Shorter command: Windows open file with default program

[NeedsMoar]

start isn't required, if you have blah.txt or movie.mp4 or whatever, just typing

movie.mp4

Will open in default. Start is only rarely needed.
If the file isn't associated with anything, it'll show the "open with..." dialog which is easier than assoc and ftype for most people.
If you're the kind of crazy that thinks they can do a better job dishing out process priorities than the OS can schedule them, go ahead and start firefox with realtime priority and watch the fail. This used to be needed sometimes (back when we had one core) but these days it just interferes with the scheduler.
If you're running a Threadripper or Epyc with L3_SRAT_AS_NUMA enabled or NPS > 1 and want to make sure some long-running hardware intensive process gets thrown onto the same node the hardware. Usually the OS will do this when it starts performing heavy access; you could also set the affinity to the CCD's cores that correspond to where that node would be if NUMA nodes are off

assoc and ftype can set new ones from the command prompt since you won't get the usual "open with" window

[stevemao]

PR welcome