Add clippy (#191)

* Organize imports

Use rustfmt to organize imports.  Resolve #162

* remove unused imports

* Fix clippy complaints

* add clippy github action

* remove comment for @arnaucube

src/lib.rs

@@ -1,3 +1,5 @@
+#![allow(clippy::get_first)]
+
 pub mod backends;
 pub mod constants;
 pub mod frontend;