Automated pypi upload & speed gain

This releases introduces new CI/CD actions to further automate the release to pypi. It also brings forth some 50% speed gain to the code.

Bug fix: prob_mk_n

This fixes a bug with the matrix prob_mk_n, which affected small timeseries. The matrix now matches Gilbert (1988).

First release

This is the first public release of the mannkendall (Python) code. For the full documentation, go to: https://mannkendall.github.io/Python