docs: improve README (#296)

Author: bolinocroustibat

README.md

@@ -1,5 +1,10 @@
+![udata-hydra](banner.png)
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 # udata-hydra 🦀
 
+[![CircleCI](https://circleci.com/gh/datagouv/hydra.svg?style=svg)](https://circleci.com/gh/datagouv/hydra)
+[![License: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](https://opensource.org/licenses/MIT)
+
 `udata-hydra` is an async metadata crawler for [data.gouv.fr](https://www.data.gouv.fr).
 
 URLs are crawled via _aiohttp_, catalog and crawled metadata are stored in a _PostgreSQL_ database.