added "code style: black"
@@ -21,6 +21,7 @@ some of its algorithms could be broken using side-channel attacks.
* * *
+[![Code style: black](https://img.shields.io/badge/code%20style-black-000000.svg)](https://github.com/psf/black)
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[![ReadtheDocs](https://img.shields.io/readthedocs/btclib.svg)](https://btclib.readthedocs.io)
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