Polish skpm-test
- [x] add watch mode
- [x] add `test.only`
- [x] add `test.skip`
- [ ] ~add `describe`, `describe.only`, `describe.skip`~
- [ ] add timing information
- [x] fix watch mode when adding and removing files
- [x] overwrite previous result in watch mode
- [x] in watch mode, press `enter` to trigger a new build and `q` to quit
- [x] capture the logs and display them in the right place (next to each test)
- [ ] documentation
- [x] find a story for async tests
- [ ] ~add `beforeAll`, `afterAll`, `beforeEach` and `afterEach`~
