Fix Codecov CI: add secret token

Author: art-w

.github/workflows/coverage.yml

@@ -30,6 +30,8 @@ jobs:
 
       - name: Checkout code
         uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
 
       - name: Use OCaml ${{ matrix.ocaml-compiler }}
         uses: ocaml/setup-ocaml@v2
@@ -46,6 +48,7 @@ jobs:
         run: opam exec -- dune runtest --instrument-with bisect_ppx
 
       - name: Send coverage report to Codecov
-        run: opam exec -- bisect-ppx-report send-to Codecov
+        run: opam exec -- bisect-ppx-report send-to Codecov --verbose
         env:
+          CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}
           PULL_REQUEST_NUMBER: ${{ github.event.number }}