2022.1

• Added accuracy unit tests, which can be used systematically
  using the pyvkfft-test installed script
• An extensive testing is now made before official releases,
  evaluating all type of transforms (c2c, r2c, dct, 1, 2 and 3D,
  in and out-of-place, norm 0 and 1), different GPUs, both OpenCL
  and CUDA, etc... Comparison is made against pyfftw, scipy or numpy.
• Update to VkFFT 1.2.21, with support for DCT types 1, 2, 3 and 4,
  also fixing a number of issues (see closed issues at
  https://github.com/DTolm/VkFFT/issues), and passing all tests
  on different GPUs (OpenCL and CUDA, AMD and nVidia)
• Raise a RuntimeError if the VkFFTApp initialisation or the
  GPU kernel launch fails, with the corresponding VkFFT error.
• [BUG] Correct inverse FFT calculation using pyvkfft.fft.ifftn()
• Installation from source using 'python setup.py install' is now
  disabled - 'pip install' should always be used.
• Added config.USE_LUT and config.FFT_CACHE_NB variables, which
  can be used to modify the default behaviour, and can also be set
  e.g. with the PYVKFFT_USE_LUT environment variable.