Workflow updates

[TimHess]

• separate build and deploy as unique jobs (so we can re-run deployment to staging after a stage/prod swap)
• update action versions
• align styles with other Steeltoe GH Actions

[github-actions]

Preview link: https://docs-steeltoe-pr-356.azurewebsites.net

• Your changes have been deployed to the preview site. The preview site will update as you add more commits to this branch.
• The preview link is shareable, but will be deleted when the pull request is merged or closed.

Need to pair with a custom main site address?

A team member can use this az CLI command, replacing and for valid numbers:

az webapp config appsettings set --resource-group steeltoe --name docs-steeltoe --slot pr-<this-PR-number> --settings mainsite_host=https://www-steeltoe-pr-<other-pr-number>.azurewebsites.net

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