Gradle scaffolding doesn't work with Kotlin based build.gradle.kts or settings.gradle.kts

[mcanalesmayo]

As stated in the Gradle scaffolding reference, it looks for a build.gradle or settings.gradle file, otherwise the scaffolding will fail. This makes the scaffolding not support projects with Kotlin based build scripts, which are named build.gradle.kts and settings.gradle.kts.
The issue happens here: https://github.com/habitat-sh/core-plans/blob/master/scaffolding-gradle/lib/scaffolding.sh#L209-L215

_confirm_scaffolding() {
  if [[ -f build.gradle || -f setttings.gradle ]]; then
    return 0
  else
    exit_with "Gradle Scaffolding cannot find build.gradle or settings.gradle" 5
  fi
}