chore: implement require-await eslint rule (#1095)

.eslintrc.js

lib/manager/index.js

lib/manager/npm/detect.js

lib/manager/npm/registry.js

lib/platform/gitlab.js

lib/workers/pr/index.js

lib/workers/repository/upgrades.js

test/config/presets.spec.js

test/platform/github.spec.js

test/platform/gitlab.spec.js

test/workers/branch/lock-files.spec.js

...rkers/repository/onboarding/pr/config-description.spec.js

.../workers/repository/onboarding/pr/errors-warnings.spec.js

test/workers/repository/onboarding/pr/pr-list.spec.js