io.readdir is not iterable with ipairs

io.readdir from the new sandboxing is not iterable with ipairs, the only way i found is to use the `lines` method.

example:
```lua
local files = io.readdir("@myResource/")
for file in files:lines() do
    print(file) -- Process each file
end
```

probably currently missing a correct implementation for ipairs and pairs