resolves #36 check extname on cmd0 only
The antora collector extension failed on windows to add .bat if I use e.g. the following configuration:
ext:
collector:
run:
command: gradlew :my.project.api:generateDocs
local: true
In this case the "extension" is determined to be ".api" as the whole command is passed. With this change only "gradlew" is passed and then it works.