Update README.md

Author: Sceki

README.md

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 Kessler is a Python package for simulation-based inference and machine learning for space collision avoidance and assessment. It is named in honor of NASA scientist [Donald J. Kessler](https://en.wikipedia.org/wiki/Donald_J._Kessler) known for proposing the [Kessler syndrome](https://en.wikipedia.org/wiki/Kessler_syndrome).