Docs for Command line option `-l g=mod`

[Albert Krewinkel <albert+lua@...>]

The standalone interpreter of Lua 5.4 not only supports the `-l mod`
option to load a module, but also this pattern:

>  -l g=mod  require library 'mod' into global 'g'

The feature is listed in the usage instructions of the `lua` standalone
interpreter. However, the feature is not mentioned in the manual; I
assume that may be an oversight.

-- 
Albert Krewinkel
GPG: 8eed e3e2 e8c5 6f18 81fe  e836 388d c0b2 1f63 1124