Generate `.pyi` files for type inference compatibility

[timblakely]

Currently Pylance - the language server used by the VSCode python extension - doesn't play nice with the cpython compiled shared object files:

However, if you use mypy's stubgen program you can automatically generate .pyi files that allow the internal types to be exposed:

cd $(dirname $(python3 -c "import tensorstore; print(tensorstore.__file__)")) && stubgen -p tensorstore -o ../

Would be nice to ship these inside the pypi package.

[stillwalker1234]

+1