Support Pagination in Get Issues command

[erichexter]

It looks like the issues code does not support pagination, which means by default the api will only return 30 items. https://github.com/Iristyle/Posh-GitHub/blob/master/Posh-Github.psm1#L170

The github api does provide the links header so that its clear when you need to call for more data.
https://developer.github.com/guides/traversing-with-pagination/ https://developer.github.com/v3/#pagination

Is this something you would like the commands to support? If so I would be willing to contribute some work, at least on the issues command. I am not sure what other commands would need pagination, but issues are typically the one thing that grows pretty big over time, if your looking at closed issues.