Add a warning / label to the Beta branch page

[sscchan]

We have a staging deployment "maps to Beta branch" that deploys beta code to pre-production.
We need this "beta" page clearly communicate that it is a beta version.

[GuessWhoSamFoo]

This may not be necessary via Netlify if the preview deployment is on a different autogenerated domain.

[sscchan]

@GuessWhoSamFoo I believe https://new-hope-calculator.netlify.com/ is used everytime by netlify. So there's a danger of users accidentally bookmarking it.

[GuessWhoSamFoo]

We should be using deploy previews instead.

[sscchan]

The stable https://new-hope-calculator.netlify.com/ urls is intended for longer term beta testers to give us feedback (usability, logic, etc) before you push it to Production.

Deploy previews are definitely useful for individual developers to sanity check any new pushes.

[sscchan]

We'll be closing this once I can get access to Netify to add the environment variables to uniquely identify Beta.