Replace Coveralls with Codecov

Shitstorm source: lemurheavy/coveralls-public#632

Author: ryukinix

.github/workflows/test.yml

@@ -53,8 +53,10 @@ jobs:
       with:
           infile: coverage.out
           outfile: coverage.lcov
-    - name: Coveralls
-      uses: coverallsapp/github-action@v1.0.1
+    - name: Codecov
+      uses: codecov/codecov-action@v1
       with:
-          github-token: ${{ secrets.GITHUB_TOKEN }}
-          path-to-lcov: coverage.lcov
+        token: ${{ secrets.CODECOV_TOKEN }}
+        file: ./coverage.lcov
+        flags: unittests
+        fail_ci_if_error: true