Options for failing workflows

Summary

Added new inputs to enable failing a workflow for coverage decreases and/or if coverage below a threshold.

Closes #21

[ ] Bug fix (non-breaking change which fixes an issue)
[x] New feature (non-breaking change which adds functionality)
[ ] Improvements to existing code, such as refactoring or optimizations (non-breaking)
[ ] Breaking change (fix or feature that would cause existing functionality to change)
[x] I have read the CONTRIBUTING document.
[x] My code follows the code style of this project.
[x] My change requires a change to the documentation.
[x] I have updated the documentation accordingly.
[x] I have added tests to cover my changes.
[x] All new and existing tests passed.