feat: added doc badges

README.md

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+[![format + lint + test](https://github.com/onechronos/symbologyl2/actions/workflows/test.yml/badge.svg)](https://github.com/onechronos/symbologyl2/actions/workflows/test.yml)
+[![Coverage Status](https://coveralls.io/repos/github/onechronos/symbologyl2/badge.svg)](https://coveralls.io/github/onechronos/symbologyl2)
+[![Docs](https://img.shields.io/docsrs/symbologyl2)](https://docs.rs/symbologyl2/)
+[![Crates.io](https://img.shields.io/crates/v/symbologyl2)](https://crates.io/crates/symbologyl2)
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 # Symbology Normalization (symbologyl2)
 
 ## Introduction