feature: added support for command-line arguments parsing

* Adding support for command-line arguments parsing
* Adding support for multiple directories to the search paths for Lua libraries
* Using Getopt::Long instead of Getopt::Std
* Adding a new test scaffold
* Adding support for specifying the nginx path (this option might be removed in the future)
You don't need to use `.` here. Just use variable interpolation exclusively here:

```
$args .= "arg[$index]=$left_bracket$arg$right_bracket; ";
```