Add Windows (Powershell) support

[WalterWoshid]

Here is a package for anyone needing this: https://github.com/WalterWoshid/laravel-sail-for-windows

Couldn't reopen #665 for some reason.

Adding the sail.ps1 script to the composer.json bin section won't work, because Composer converts it into a bash script. I have added a new publish item which copies the sail.ps1 file to the bin folder of Composer with the laravel-assets tag. This should mimick Composers binary copying.

[taylorotwell]

Thanks for your pull request to Laravel!

Unfortunately, I'm going to delay merging this code for now. To preserve our ability to adequately maintain the framework, we need to be very careful regarding the amount of code we include.

If possible, please consider releasing your code as a package so that the community can still take advantage of your contributions!

If you feel absolutely certain that this code corrects a bug in the framework, please "@" mention me in a follow-up comment with further explanation so that GitHub will send me a notification of your response.

[WalterWoshid]

Hi, thanks for the feedback, I had a feeling that the codebase was very slim, which I understand. I'd be happy to make a package out of it :)

Edit: Here is a package for anyone needing this: https://github.com/WalterWoshid/laravel-sail-for-windows