add: use ws interp for nyq grid

[Tieqiong]

closes #112

@sbillinge please check if this is good, thanks

maybe we should add new tests for this...

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.10%. Comparing base (792e22d) to head (2f2cd1e).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #263   +/-   ##
=======================================
  Coverage   95.10%   95.10%           
=======================================
  Files          23       23           
  Lines        1123     1123           
=======================================
  Hits         1068     1068           
  Misses         55       55           

Files with missing lines	Coverage Δ
tests/test_fitdataset.py	98.27% <100.00%> (ø)