ENH: Add type annotation information

Add type annotation information: add the `py.typed` file and distribute
the type information with the package by adding the corresponding entry
in the `pyproject.toml` file so that third-party tools can use the DIPY
type annotation information.

Documentation:
https://typing.readthedocs.io/en/latest/spec/distributing.html#packaging-typed-libraries

Author: jhlegarreta

pyproject.toml

@@ -122,6 +122,9 @@ version-file = "src/nifreeze/_version.py"
 # Developer tool configurations
 #
 
+[tool.setuptools.package-data]
+"nifreeze" = ["py.typed"]
+
 [tool.ruff]
 line-length = 99
 target-version = "py310"