Kotlin extensions and support for suspending continuations.

New Kotlin extensions such as property .l to close tag in Kotlin, instead of .__()

New builder .suspending() to allow the use of continuations in Kotlin with suspending functions doing await.

Solved Issue 105 - new attributes in globalEventAttributes included in new release 1.0.15 of HtmlApiFaster.

New unit tests to check multi-threaded scenarios.

Update documentation mentioning setIndentation() and correct use of threadsafe()