Add py.typed Marker (#2904)

* feat(typehinting): add `py.typed` marker to package

This will allow static type checkers to recognized the package's type hints per PEP-561

Fixes issue #2903

* fix(package-data): add `py.typed` to `package_data`

* Add newline to end of py.typed

* feat(setuptools): add type hint files to `MANIFEST.in` and set `zip_safe=False`

`mypy` requires packages built with `setuptools` use the `zip_safe=False` option so it can find the package and `*.pyi` and `*.typed` files be added to the `MANIFEST.in` so they are included in the `sdist`.

See https://mypy.readthedocs.io/en/latest/installed_packages.html#creating-pep-561-compatible-packages

* Add newline to end of MANIFEST.in

Co-authored-by: Hendry, Adam <adam.hendry@medtronic.com>
Co-authored-by: Andras Deak <deak.andris@gmail.com>

MANIFEST.in

@@ -2,3 +2,6 @@
 include LICENSE
 recursive-exclude doc *.rst
 recursive-exclude doc *.py
+# Include type hinting files
+global-include *.pyi
+global-include *.typed

pyvista/py.typed

@@ -0,0 +1 @@
+partial\n

setup.py

@@ -58,6 +58,9 @@
     url='https://github.com/pyvista/pyvista',
     keywords='vtk numpy plotting mesh',
     package_data={
+        'pyvista': [
+            'py.typed',
+        ],
         'pyvista.examples': [
             'airplane.ply',
             'ant.ply',
@@ -84,4 +87,5 @@
         'io': ['meshio>=5.2'],
         'jupyter': ['ipyvtklink', 'pythreejs'],
     },
+    zip_safe=False,
 )