- Add doctest coverage also

Author: ChrisRega

.github/workflows/coverage.yml

@@ -29,6 +29,7 @@ jobs:
       - name: Run grcov
         env:
           PROJECT_NAME: "json-diff"
+          RUSTDOCFLAGS: "-Cinstrument-coverage -Ccodegen-units=1 -Copt-level=0 -Clink-dead-code -Coverflow-checks=off -Zpanic_abort_tests -Cpanic=abort"
           RUSTFLAGS: "-Cinstrument-coverage -Ccodegen-units=1 -Copt-level=0 -Clink-dead-code -Coverflow-checks=off -Zpanic_abort_tests -Cpanic=abort"
           CARGO_INCREMENTAL: 0
         run: |