build: Update stryker-api requirement to ^0.12.0 (#598)
build: Update stryker-api requirement to ^0.12.0 (#598)

Updates the requirements on [stryker-api](https://github.com/stryker-mutator/stryker) to permit the latest version.
- [Commits](https://github.com/stryker-mutator/stryker/commits/stryker@0.12.0)
stryker-mutator/stryker,stryker-mutator/stryker,stryker-mutator/stryker