Add Lua os library section

[sundb]

in redis/redis#12971 we expose a new Lua os api os.clock().

[netlify]

👷 Deploy request for redis-doc pending review.

Visit the deploys page to approve it

Name	Link
🔨 Latest commit	be65125

[zuiderkwast]

LGTM.

I wonder why the other date and time functions os.date, os.time and os.timediff were not exposed. Apart from those, we now seem to allow all standard library functions except the ones that access the file system and IO. I wasn't involved in the original PR though.

[sundb]

@zuiderkwast At first, i wondered whether to expose like o.date and similar non-dangerous Lua api as well.
we should expose a Lua api because it can complement something we can't do, like time escaping, but the
reset of api doesn't, IMHO, i don't think we should expose it just because it exists.

[zuiderkwast]

IMHO, i don't think we should expose it just because it exists

We expose the other standard libraries. For those who know Lua from before, they might assume that all standard library functions are available (except the dangerous ones). But I have no strong opinion.