Add codecov job.

Author: hoolioh

.github/workflows/build.yml

@@ -5,6 +5,7 @@ on:
   push:
     branches:
       - main
+      - julio/codecov
 
 jobs:
   build:
@@ -30,3 +31,21 @@ jobs:
         uses: qard/heaviest-objects-in-the-universe@v1
         with:
           github-token: ${{ secrets.GITHUB_TOKEN }}
+  coverage:
+    runs-on: ubuntu-latest
+    env:
+      CARGO_TERM_COLOR: always
+    steps:
+      - uses: actions/checkout@v4
+      - name: Install Rust
+        run: rustup update stable
+      - name: Install cargo-llvm-cov
+        uses: taiki-e/install-action@cargo-llvm-cov
+      - name: Generate code coverage
+        run: cargo llvm-cov --all-features --workspace --lcov --output-path lcov.info
+      - name: Upload coverage to Codecov
+        uses: codecov/codecov-action@v3
+        with:
+          token: ${{ secrets.CODECOV_TOKEN }} # not required for public repos
+          files: lcov.info
+          fail_ci_if_error: true