updated links

Author: mhubii

README.md

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 # Sparsity-preserving gradient utility tools for PyTorch
-[![Python tests](https://github.com/cai4cai/torchsparsegradutils/actions/workflows/python-package.yml/badge.svg)](https://github.com/cai4cai/torchsparsegradutils/actions/workflows/python-package.yml) ![License](https://img.shields.io/github/license/cai4cai/torchsparsegradutils) ![Code Style: Black](https://img.shields.io/badge/code%20style-black-000000.svg)
+[![Python tests](https://github.com/cai4cai/torchsparsegradutils/actions/workflows/python-package.yml/badge.svg)](https://github.com/cai4cai/torchsparsegradutils/actions/workflows/python-package.yml) [![License](https://img.shields.io/github/license/cai4cai/torchsparsegradutils)](https://github.com/cai4cai/torchsparsegradutils?tab=Apache-2.0-1-ov-file#readme) [![Code Style: Black](https://img.shields.io/badge/code%20style-black-000000.svg)](https://github.com/psf/black)
 
 A collection of utility functions to work with PyTorch sparse tensors. This is work-in-progress, here be dragons.