FR: adding a setRange() function to AudioProcessorValueTreeState

After adding my comment here, I worked out that you can get default range and interval behaviour by using a NormalisableRange constructor, with a skew factor of 1.0.

I fully see the value of keeping a set range too, however granularity was an issue for me as my values are really small - this is where the NormalisableRange helped me.

See AudioProcessorValueTreeState range values