docs(l1, l2): update README.md (#1278)

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Closes #issue_number

README.md

@@ -1,5 +1,7 @@
 # ethrex
 
+Ethereum Rust Execution L1 and L2 client.
+
 [![Telegram Chat][tg-badge]][tg-url]
 [![license](https://img.shields.io/github/license/lambdaclass/ethrex)](/LICENSE)