Lighthouse audit

[xjensen]

Several small changes to increase lighthouse scores. Also...

• I discovered a bug in the SPEI map renderer. Fixed.
• Some of these updates will benefit from corresponding content updates, which are queued up in staging.
• I'll need to do some investigation to get the last couple accessibility points. We can get it to 100 by removing keyboard nav from the new data-viz, but that's cheating.
• We will need to do some work in the Design System to remove the CSS sourcemap warnings.

[github-actions[bot]]

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