add rustfmt, rustdoc and clippy to githubs workflow

Author: hellow554

.github/workflows/ci.yml

@@ -24,9 +24,12 @@ jobs:
     steps:
       - uses: actions/checkout@v2
       - uses: dtolnay/rust-toolchain@stable
+      - run: cargo fmt --all -- --check
       - run: cargo check --no-default-features
       - run: cargo check --no-default-features --features "use_alloc"
       - run: cargo test
+      - run: RUSTDOCFLAGS="-Dwarnings" cargo doc --all-features
+      - run: cargo clippy --all -- -Dwarnings
 
   # https://github.com/rust-lang/crater/blob/9ab6f9697c901c4a44025cf0a39b73ad5b37d198/.github/workflows/bors.yml#L125-L149
   end-success: