feat: re-export Url in starknet-providers (#519)

This type is needed to initialize a JSON-RPC client. Having this type
re-exported makes it eaiser to use, as applications would not have to
import the `url` crate themselves nor worry about the version.

Author: xJonathanLEI

starknet-providers/src/lib.rs

@@ -13,3 +13,6 @@ pub use jsonrpc::JsonRpcClient;
 
 mod any;
 pub use any::AnyProvider;
+
+// Re-export
+pub use url::Url;