Catsmoothing

Changed

- Improved the code performance by creating a global thread pool that is
shared across all functions that run in parallel. This avoids creating
a new thread pool for each function call, which was causing a performance
overhead.
- Improved the performance of the `gaussian_smoothing` function by using
a more efficient algorithm to compute the convolution of the input
data with a Gaussian kernel.

Fixed

- Fix the `smooth_linestrings` function to correctly handle returning
multiple `LineString` geometries when a list of `LineString` geometries
is passed as input.

This is a major release with breaking changes. The codebase has been
written from scratch in Rust and the Python bindings have been updated
to reflect the changes in the underlying implementation.

Changed

- The `bc_types` argument of `CatmullRom` class has been renamed to
`bc_type` and custom boundary conditions have been removed. The
available boundary conditions are `'natural'`, `'closed'`, and
`'clamped'`.
- The `smooth_linstring` function has been renamed to `smooth_linestrings`.
This function now handles a list of `LineString` geometries instead of a
single geometry. The code runs in parallel in Rust and is significantly
faster than the previous implementation. If a single `LineString` geometry is passed a single `LineString` geometry is returned, otherwise a list of `LineString` geometries is returned.
- The `compute_tangents` has been renamed to `linestrings_tangent_angles`.
This function now handles a list of `LineString` geometries and returns
the tangent angles at each vertex of the input geometries. The code runs
in parallel in Rust and is significantly faster than the previous. If a single `LineString` geometry is passed a single array of tangent angles is returned, otherwise a list of arrays is returned.

Added

- Add a new boundary condition for the `CatmullRom` class called `'clamped'`,
which allows anchoring the first and last points of the curve to the first
and last control points. This is particularly useful for smoothing
`MultiLineString` geometries where the first and last points of each
line segment must remain connected to the previous and next line segment.

Changed

- Freeze attributes of `CatmullRom` since they are not supposed to be changed,
once the class is instantiated. If needed, a new instance should be created.

- Initial release.