🔧 Add requirements-dev.txt

Added requirements.txt and requirements-dev.txt as it is not yet
possible to install only dependencies from pyproject.toml.

See pypa/pip#11440 for more information.

requirements-dev.txt

@@ -0,0 +1,16 @@
+# This file contains optional dependencies for the
+# `development`, such as updating or testing the
+# source codes of the project.
+
+# In this case, you should install all dependencies
+# listed in this file as well as requirements.txt.
+
+# For example:
+# $ python -m pip install [-U] -r requirements.txt
+# $ python -m pip install [-U] -r requirements-dev.txt
+
+hatch
+ruff
+mypy
+black
+pytest