H3ronpy

- Improved documentation of the raster modules.
- Validate bounds of input raster arrays to be within WGS84 lat/lon coordinates.
- Make the GeoSeries-returning function show up in the `h3ronpy.pandas.vector` module.

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In this release the project migrated to the [arrow memory model](https://arrow.apache.org/) and switched from the [h3ron library](https://github.com/nmandery/h3ron) to the Rust implementation of H3 named [h3o](https://github.com/HydroniumLabs/h3o). This comes along with safer code and [performance improvements](https://github.com/nmandery/rasterh3/issues/1). Although `h3ronpy` is no longer build on the `h3ron` rust crate, the name remains.

As a result of these migrations, the Python API has completely changed. Due to this it is easier to refer to the
new documentation than listing the changes here. That is another aspect of these changes - there now exists a sphinx generated
documentation.

Other changes:

- Upgrade from pyo3 0.18 to 0.19.

* Upgrade from pyo3 0.17 to 0.18.
* Support minimum supported python version to 3.7 again

* Directly support GeoSeries in vector to H3 conversion by automatically exchanging geometries using WKB. [7](https://github.com/nmandery/h3ronpy/pull/7)
* Raise minimum supported python version to 3.8.
* `intersecting` argument for `geodataframe_to_h3` to also include cells which are only intersecting with the geometry, but whose centroid is not contained in the geometry.

* Upgrade to h3ron v0.16.0.
* Reduced the durations the GIL is held.

- Dependency upgrades incl. upgrade to H3 v4.0.0 / h3ron v0.15.0.
- The migration to H3 v4.0.0 comes with renaming a few functions to follow H3 conventions:
- In `h3ronpy.op` module:
- `kring_distances` -> `grid_disk_distances`
- `kring_distances_agg` -> `grid_disk_distances_agg`
- `kring_distances_agg_np` -> `grid_disk_distances_agg_np`