add badges to readme

Author: rrsettgast

README.md

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 HPCReact
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+[![DOI](https://zenodo.org/badge/880512605.svg)](https://doi.org/10.5281/zenodo.15743474)
+[![CI](https://github.com/GEOS-DEV/HPCReact/actions/workflows/continuousIntegration.yml/badge.svg)]
+[![codecov](https://codecov.io/github/geos-dev/hpcreact/graph/badge.svg?token=VMYDFYCT3Q)](https://codecov.io/github/geos-dev/hpcreact)
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 HPCReact is a collection of inline, device-callable functions for modeling pointwise chemical reactions.
 It is designed to provide building blocks for constructing computational kernels that update chemical states in simulations involving reactive chemistry.