Updated aleph-client readme (#846)

aleph-client/README.md

@@ -1,7 +1,20 @@
-### Metadata
+# API for [aleph-node](https://github.com/Cardinal-Cryptography/aleph-node) chain.
 
-We use autogenerated metadata in this lib. To generate it you will need subxt-cli. See [here](https://github.com/paritytech/subxt) for instructions how to install it.
-The metadata is generated by:
-```bash
-subxt codegen --derive Clone Debug Eq PartialEq | rustfmt --edition=2021 > src/aleph_zero.rs
-```
+This crate provides a Rust application interface for submitting transactions to `aleph-node` chain.
+Most of the [pallets](https://docs.substrate.io/reference/frame-pallets/) are common to any
+[Substrate](https://github.com/paritytech/substrate) chain, but there are some unique to `aleph-node`,
+e.g. [`pallets::elections::ElectionsApi`](./src/pallets/elections.rs).
+
+## Build
+
+Just use `cargo build` or `cargo build --release`, depends on your usecase.
+
+## Contributions
+
+All contributions are welcome, e.g. adding new API for pallets in `aleph-node`. 
+
+## Metadata
+
+`aleph-client` uses [`subxt`](https://github.com/paritytech/subxt) to communicate with a Substrate-based chain which
+`aleph-node` is. In order to provide a strong type safety, it uses a manually generated file [`aleph_zero.rs`](src/aleph_zero.rs)
+which refers to top of the `main` branch in `aleph-node` repository. See more info [here](docker/README.md).