ci: add upload coverage report to codecov

.github/workflows/codecov.yml

@@ -0,0 +1,40 @@
+name: Upload Code Coverage
+
+on:
+  push:
+  pull_request:
+
+env:
+  CARGO_TERM_COLOR: always
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v3
+      - uses: dtolnay/rust-toolchain@stable
+        with:
+          toolchain: nightly
+          components: rustfmt, llvm-tools-preview
+      - name: Build
+        run: cargo build --release
+        env:
+          CARGO_INCREMENTAL: "0"
+          RUSTFLAGS: "-Cinstrument-coverage"
+          RUSTDOCFLAGS: "-Cinstrument-coverage"
+      - name: Test
+        run: cargo test --all-features --no-fail-fast
+        env:
+          CARGO_INCREMENTAL: "0"
+          RUSTFLAGS: "-Cinstrument-coverage"
+          RUSTDOCFLAGS: "-Cinstrument-coverage"
+      - name: Install grcov
+        run: if [[ ! -e ~/.cargo/bin/grcov ]]; then cargo install grcov; fi
+      - name: Run grcov
+        run: grcov . --binary-path target/debug/deps/ -s . -t lcov --branch --ignore-not-existing --ignore '../**' --ignore '/*' -o coverage.lcov
+      - uses: codecov/codecov-action@v3
+        with:
+          files: ./coverage.lcov
+          flags: rust
+          fail_ci_if_error: true # optional (default = false)