Added SunOS (tested against OmniOS)

[pstumpe]

requires "top" package to be installed for parsing memory/swap info (cmd "pkg install top")
Signed-off-by: pstumpe github@stumpe.ws

[joshtrichards]

Is your implementation at all related to the one linked to from #263 by @dertuxmalwieder (they haven't submitted a PR, but did reference the issue in their fork's commit so I saw it pop up over there).

dertuxmalwieder@ba979bf

EDIT: Nevermind! Thank you for your PR. There was a prior PR, but it was built on an older implementation of serverinfo. I overlooked the full history.

[dertuxmalwieder]

I wish that my first approach would have been merged. ;-)

[pstumpe]

Actually I took a look at the PRs from @dertuxmalwieder and tried to fix a few problems / errors in the code together with some small changes (e.g. as to show ZFS filesystems instead of actual discs).

[kesselb]

Thanks for your pull request 👍

Please add tests for your implementation. You may use the tests I wrote for the other SunOS / OmniOS as a starting point: https://github.com/nextcloud/serverinfo/compare/feat/sun-os