add badges

Author: florian-huber

README.md

@@ -1,3 +1,7 @@
+![GitHub License](https://img.shields.io/github/license/matchms/graphconstructor)
+[![PyPI](https://img.shields.io/pypi/v/graphconstructor?color=teal)](https://pypi.org/project/graphconstructor/)
+![GitHub Workflow Status](https://img.shields.io/github/actions/workflow/status/matchms/graphconstructor/CI_build_and_matrix_tests.yml?branch=main)
+
 <img src="/docs/graphconstructor_logo.png" alt="Alt Text" width="600">
 
 # graphconstructor