Update GitHub Pages deployment workflow

[joelhulen]

Update GitHub Pages deployment workflow

Details on the issue fix or feature implementation

Hardens GitHub Pages deployment and adds the custom domain name configuration (cname).

Confirm the following

• I started this PR by branching from the head of the default branch
• I have targeted the PR to merge into the default branch
• I have included unit tests for the issue/feature
• I have included inline docs for my changes, where applicable
• I have successfully run a local build
• I have provided the required update scripts, where applicable
• I have updated relevant docs, where applicable

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