Move to GitHub Actions from Azure DevOps

[TheYorkshireDev]

Move CI and CD from Azure DevOps to GitHub Actions. Azure DevOps feels a lot more cumbersome than when it once did and I'd prefer to consolidate CI/CD within GitHub.

This first step should just do a "lift and shift" so pushes/merges to master kicks off a build that uploads to Netlify. Any PRs should push to the staging site currently an Azure storage account with CDN.

Acceptance Criteria

• New branches don't kick off a build
• PR kicks off a build and deploys to stage
• Push to master branch builds and deploys to Netlify
• Merging a PR into master branch builds and deploys to Netlify