Pylops

* Fixed ``pylops.optimization.basic.lsqr``, ``pylops.optimization.sparsity.ISTA``, and
``pylops.optimization.sparsity.FISTA`` to work with cupy arrays. This change was required
by how recent cupy versions handle scalars, which are not converted directly into float types,
rather kept as cupy arrays.
* Fixed bug in ``pylops.waveeqprocessing.Deghosting`` introduced in
commit [7e596d4](https://github.com/PyLops/pylops/commit/7e596d4dad3793d6430204b7a9b214a9dc39616c)

* Refractored `pylops.utils.dottest`, and added two new optional input parameters
(``atol`` and ``rtol``)
* Added optional parameter ``densesolver`` to ``pylops.LinearOperator.div``

* !DELETED! due to a mistake in the release process

* Added `NMO` example to gallery
* Extended `pylops.basicoperators.Laplacian` to N-dimensional arrays
* Added `forward` kind to `pylops.basicoperators.SecondDerivative` and
`pylops.basicoperators.Laplacian`
* Added `chirp-sliding` kind to `pylops.waveeqprocessing.seismicinterpolation.SeismicInterpolation`
* Fixed bug due to the new internal structure of `LinearOperator` submodule introduced in `scipy1.8.0`

* Added `pylops.utils.describe.describe` method
* Added `fftengine` to `pylops.waveeqprocessing.Marchenko`
* Added `ifftshift_before` and `fftshift_after` optional input parameters in
`pylops.signalprocessing.FFT`
* Added `norm` optional input parameter to `pylops.signalprocessing.FFT2D` and
`pylops.signalprocessing.FFTND`
* Added `scipy` backend to `pylops.signalprocessing.FFT` and
`pylops.signalprocessing.FFT2D` and `pylops.signalprocessing.FFTND`
* Added `eps` optional input parameter in
`pylops.utils.signalprocessing.slope_estimate`
* Added pre-commit hooks
* Improved pre-commit hooks
* Vectorized `pylops.utils.signalprocessing.slope_estimate`
* Handlexd `nfft<nt` case in `pylops.signalprocessing.FFT` and
`pylops.signalprocessing.FFT2D` and `pylops.signalprocessing.FFTND`
* Introduced automatic casting of dtype in `pylops.MatrixMult
* Improved documentation and definition of optinal parameters
of `pylops.Spread`
* Major clean up of documentation and mathematical formulas
* Major refractoring of the inner structure of `pylops.signalprocessing.FFT` and
`pylops.signalprocessing.FFT2D` and `pylops.signalprocessing.FFTND`
* Reduced warnings in test suite
* Reduced computational time of `test_wavedecomposition` in the test suite
* Fixed bug in `pylops.signalprocessing.Sliding1D`,
`pylops.signalprocessing.Sliding2D` and
`pylops.signalprocessing.Sliding3D` where the `dtype` of the Restriction
operator is inffered from `Op`
* Fixed bug in `pylops.signalprocessing.Radon2D` and
`pylops.signalprocessing.Radon3D` when using centered spatial axes
* Fixed scaling in `pylops.signalprocessing.FFT` with `real=True` to pass the
dot-test

* Added `pylops.utils.estimators` module for trace estimation
* Added `x0` in `pylops.optimization.sparsity.ISTA` and
`pylops.optimization.sparsity.FISTA` to handle non-zero initial guess
* Modified `pylops.optimization.sparsity.ISTA` and
`pylops.optimization.sparsity.FISTA` to handle multiple right hand sides
* Modified creation of `haxis` in `pylops.signalprocessing.Radon2D` and
`pylops.signalprocessing.Radon3D` to allow for uncentered spatial axes
* Fixed `_rmatvec` for explicit in `pylops.LinearOperator._ColumnLinearOperator`