Add Lua os library section (#2671)

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

docs/interact/programmability/lua-api.md

@@ -670,6 +670,7 @@ The following [standard Lua libraries](https://www.lua.org/manual/5.1/manual.htm
 * The [_String Manipulation (string)_ library](https://www.lua.org/manual/5.1/manual.html#5.4)
 * The [_Table Manipulation (table)_ library](https://www.lua.org/manual/5.1/manual.html#5.5)
 * The [_Mathematical Functions (math)_ library](https://www.lua.org/manual/5.1/manual.html#5.6)
+* The [_Operating System Facilities (os)_ library](#os-library)
 
 In addition, the following external libraries are loaded and accessible to scripts:
 
@@ -678,6 +679,18 @@ In addition, the following external libraries are loaded and accessible to scrip
 * The [_cmsgpack_ library](#cmsgpack-library)
 * The [_bitop_ library](#bitop-library)
 
+### <a name="os-library"></a> _os_ library
+
+* Since version: 8.0.0
+* Available in scripts: yes
+* Available in functions: yes
+
+_os_ provides a set of functions for dealing with date, time, and system commands.
+More details can be found in the [Operating System Facilities](https://www.lua.org/manual/5.1/manual.html#5.8).
+Note that for sandbox security, currently only the following os functions is exposed:
+
+* `os.clock()`
+
 ### <a name="struct-library"></a> _struct_ library
 
 * Since version: 2.6.0