add wasm support (#700)

* get started

* make it work again

* make it compile again

* Use async-wasm-feature of jsonrpsee from the master branch

* Ensure we enable JS feature of getrandom for the wasm target

* Update subxt/src/lib.rs

* update jsonrpsee

* fix CI

* cargo fmt

* fix wasm test

* fix grumbles

* exclude wasm-tests from workspace

To avoid leaking `jsonrpsee-web` feature into the workspace

Co-authored-by: Igor Matuszewski <xanewok@gmail.com>

testing/wasm-tests/tests/wasm.rs

@@ -0,0 +1,26 @@
+#![cfg(target_arch = "wasm32")]
+
+use subxt::config::PolkadotConfig;
+use wasm_bindgen_test::*;
+
+wasm_bindgen_test::wasm_bindgen_test_configure!(run_in_browser);
+
+/// Run the tests by `$ wasm-pack test --firefox --headless`
+
+fn init_tracing() {
+    console_error_panic_hook::set_once();
+    tracing_wasm::set_as_global_default();
+}
+
+#[wasm_bindgen_test]
+async fn wasm_ws_transport_works() {
+    init_tracing();
+
+    let client =
+        subxt::client::OnlineClient::<PolkadotConfig>::from_url("ws://127.0.0.1:9944")
+            .await
+            .unwrap();
+
+    let chain = client.rpc().system_chain().await.unwrap();
+    assert_eq!(&chain, "Development");
+}