pull coverage from index.js

.gitlab-ci.yml

@@ -16,7 +16,7 @@ cov:
   script:
   - cargo build
   - cargo kcov
-  - COVERAGE=$(grep -Po 'covered":.*?[^\\]"' target/cov/index.json | grep "[0-9]*\.[0-9]" -o)
+  - COVERAGE=$(grep -Po 'covered":.*?[^\\]"' target/cov/index.js | grep "[0-9]*\.[0-9]" -o)
   - echo "Coverage:" $COVERAGE
   - mv target/cov public/
   artifacts: