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

.gitignore

@@ -1,4 +1,5 @@
 /target
 **/*.rs.bk
+**/.DS_Store
 Cargo.lock
-cargo-timing*
+cargo-timing*