Check docs and run clippy on PRs (#326)

* Check docs, clippy, test run

* test parallel CI adapted from other package; is it faster?

* Remember to download substrate

* Nightly for cargo fmt

* Standardise CI names

* fix clippy complaints

* Ensure docs are valid and export publicly accessible types

* all-targets clippy, and fix additional lint errors

* newline in ci file

tests/integration/client.rs

@@ -117,7 +117,7 @@ async fn test_iter() {
         .await
         .unwrap();
     let mut i = 0;
-    while let Some(_) = iter.next().await.unwrap() {
+    while iter.next().await.unwrap().is_some() {
         i += 1;
     }
     assert_eq!(i, 13);