Please make artifact filenames with the same pattern as other nats-io projects

[kmpm]

• nats-server uses <name>-<version>-<os>-<arch>
• natscli uses <name>-<version>-<os>-<arch>

nats-top uses a mix of - and _.
<name>-<version>_<os>_<arch>

This and zip artifacts talked about in #74 would make scripting installations a lot easier, keeping the different projects consistent.
Or at least use one of dash and underscore, not both.

While you are at it, please make the contents of the archive like the other projects mentioned above. Their archive contains a subfolder with the same name as the archive and not directly in the root of the archive like this project does.