Very interesting!
I have a few small suggestions.
1. The think that takeScreenshot would work better as a block macro (and perhaps shorten it to screenshot)
.Google home page
[name=google]
That brings it more inline with the syntax in Asciidoctor Diagram.
2. Instead of "driveBrowser", perhaps name the block "navigate" or "browse"
[browse]
$("input", name: "q").value("asciidoctor")
waitFor(5){true}
3. The examples repository is misspelled (it's missing the "c" in screenshot)
Exciting stuff!
Cheers,