ci: add code coverage job

Stolen from nymius's [pr](bitcoindevkit/bdk#1986)
on bitcoindevkit/bdk regarding the same.

Author: 110CodingP

.github/workflows/code_coverage.yml

@@ -0,0 +1,43 @@
+on: [push, pull_request]
+
+name: Code Coverage
+
+permissions: {}
+
+jobs:
+  Codecov:
+    name: Code Coverage
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          persist-credentials: false
+      - name: Install lcov tools
+        run: sudo apt-get install lcov -y
+      - name: Install Rust toolchain
+        uses: actions-rs/toolchain@v1
+        with:
+            toolchain: nightly
+            override: true
+            profile: minimal
+            components: llvm-tools-preview
+      - name: Rust Cache
+        uses: Swatinem/rust-cache@v2.7.8
+      - name: Install cargo-llvm-cov
+        run: if [[ ! -e ~/.cargo/bin/cargo-llvm-cov ]]; then cargo install cargo-llvm-cov; fi
+      - name: Make coverage directory
+        run: mkdir coverage
+      - name: Test and report coverage
+        run: cargo +nightly llvm-cov -q --doctests --branch --all-features --lcov --output-path ./coverage/lcov.info
+      - name: Generate HTML coverage report
+        run: genhtml -o coverage-report.html --ignore-errors unmapped ./coverage/lcov.info
+      - name: Coveralls upload
+        uses: coverallsapp/github-action@master
+        with:
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+      - name: Upload artifact
+        uses: actions/upload-artifact@v4
+        with:
+          name: coverage-report
+          path: coverage-report.html