Install Netlify GitHub App for PR preview

[tomkerkhove]

I've noticed Netlify is being used for hosting the content based on https://github.com/oam-dev/oam-dev.github.io/blob/dev/netlify.toml

The Netlify GitHub App could be use to build a preview of the website in a PR so that it can be reviewed as it would be deployed.

For an example, see tomkerkhove/promitor#766 which generated https://deploy-preview-766--promitor-staging.netlify.com/. I'm not using Netlify for my PROD site so it would be https://deploy-preview-766--oam.netlify.com/.

[flynnduism]

The site used Netlify for earlier dev and staging work, but the live site is actually hosted on Github Pages.

live site     -->   oam-dev.github.io
staging site  -->   oamdev.netlify.com

I'd prefer to use Netlify as well as their continuous deployment for Hugo static sites is smoother than Github Pages. Currently we have to run these steps to deploy. Plus the deploy previews you mention on pull requests is a great feature.

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@vturecek what do you think? What we have right now works. Changing would require a DNS edit.