Fixed small pitch shifting bug in SynthDef and add a parameter

[thgrund]

I have seen that there is a "dirt_pitch_shift" module in core_synths. Unfortunately it does not work as intended, because the pitch shift parameter "pitchRatio" in core_synths is called psratio and in core_modules psrate. I fixed this typo (now it is called psrate everywhere) and was able to use it successfully on the tidal side.

I also added the timeDispersion parameter for PitchShift and named it disp.

[thgrund]

Sure, that's no problem. I renamed disp to psdisp. I like these clarification, because that way you can better associate psdisp with psrate.

[telephon]

Thank you!