[Feature] Add "deploy all" button

[djeglin]

We are using this plugin for a multi-site setup but have some content that spans across the network of sites. Rather than having to manually publish each site, it would be useful to have the option of clicking a single button to redeploy all of the sites on Netlify.

I'm happy to look at making this modification, but it may take a while as I'll have to fit the change in around actual work.

Cheers all

[sjelfull]

Thanks for suggesting this feature, we will keep it in mind!