Added py.typed to signal this project uses type declarations

[juanjosegarciaripoll]

Description

When using opt_einsum in other projects, mypy complains that opt_einsum cannot be type checked. The reason is that for an installed library to be considered by mypy, a file py.typed must be installed in the root directory of the module.

Status

• [x] Ready to go

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 91.63%. Comparing base (384bb5a) to head (6aaf482).

Additional details and impacted files

[dgasmith]

@juanjosegarciaripoll gentle ping here.