Improve Rust readme header
-# Tokenizers
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+ <img src="https://huggingface.co/landing/assets/tokenizers/tokenizers-logo.png" width="600"/>
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+ <img alt="Build" src="https://github.com/huggingface/tokenizers/workflows/Rust/badge.svg">
+ <a href="https://github.com/huggingface/tokenizers/blob/master/LICENSE">
+ <img alt="GitHub" src="https://img.shields.io/github/license/huggingface/tokenizers.svg?color=blue">
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The core of `tokenizers`, written in Rust.
Provides an implementation of today's most used tokenizers, with a focus on performance and
