chore: add code coverage

.github/workflows/codecov.yml

@@ -0,0 +1,49 @@
+name: Codecov
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+    branches:
+      - main
+    types: [opened, reopened, synchronize]
+
+jobs:
+  codecov-grcov:
+    name: Generate code coverage
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: true
+    steps:
+      - name: install toolchain according to rust-toolchain
+        uses: actions-rs/toolchain@v1
+        with:
+          toolchain: nightly
+          profile: default
+          override: true
+          components: llvm-tools-preview
+      - name: Checkout sources
+        uses: actions/checkout@v2
+      - uses: Swatinem/rust-cache@v1
+      - name: Install grcov, and cache the binary
+        uses: baptiste0928/cargo-install@v1
+        with:
+          crate: grcov
+      - name: Build
+        uses: actions-rs/cargo@v1
+        with:
+          command: build
+        env:
+          RUSTFLAGS: '-Cinstrument-coverage'
+          RUSTDOCFLAGS: '-Cinstrument-coverage'
+      - name: Run tests
+        env:
+          RUSTFLAGS: '-Cinstrument-coverage'
+          RUSTDOCFLAGS: '-Cinstrument-coverage'
+          LLVM_PROFILE_FILE: 'codecov-instrumentation-%p-%m.profraw'
+        run: |
+          cargo test 
+      - name: Run grcov
+        run: grcov . --binary-path target/debug/ -s . -t lcov --branch --ignore-not-existing --ignore '../**' --ignore '/*' -o coverage.lcov
+      - name: Upload to codecov.io
+        uses: codecov/codecov-action@v1