Let's Travis check that for yarn lockfile and package.json sync

See https://yarnpkg.com/lang/en/docs/cli/check/

.travis.yml

@@ -286,6 +286,7 @@ before_install:
   - export PUBLISH=$([[ "${TRAVIS_TAG:-}" == "v${PACKAGE_JSON_VERSION}" ]] && echo "On" || echo "Off")
   - echo "Using ${JOBS} jobs"
   - yarn install --ignore-scripts
+  - yarn check --ignore-scripts --integrity
     # Bootstrap cmake to be able to run mason
   - CMAKE_URL="https://mason-binaries.s3.amazonaws.com/${TRAVIS_OS_NAME}-x86_64/cmake/${CMAKE_VERSION}.tar.gz"
   - CMAKE_DIR="mason_packages/${TRAVIS_OS_NAME}-x86_64/cmake/${CMAKE_VERSION}"