Test context configuration, documentation improvements
### Breaking changes
Replace:
```kotlin
test("Foo", yourCoroutineContext) {
// your test
}
```
by
```kotlin
test("Foo", Context(yourCoroutineContext)) {
// your test
}
```
### Suite
- Removed the 'context' parameter to 'test' and added the Context configuration (#75, !115)
### Documentation
- Removed the empty 'Best practices' section (!118)
- The documentation website now contains the reference (!119)
### Dependencies
- Kotlin 2.1.0