Merge branch 'requirements-info' into 'main'

Add minimal versions and licensing information for requirements

See merge request !7

requirements.txt

-numpy
+numpy >= 1.20.0 # BSD

tests/requirements.txt

-black
-build
-flake8
 autopep8 >= 1.7.0 # MIT
-pylint
-pytest
-pytest-cov
+black >= 22.0.0 # MIT
+build >= 0.8.0 # MIT
+flake8 >= 5.0.0 # MIT
+pylint >= 2.15.0 # GPLv2
+pytest >= 7.0.0 # MIT
+pytest-cov >= 3.0.0 # MIT