Add support for different time ranges (e.g. days, weeks, months)

[bvaughn]

• Replace month-centric index+duration with start/stop date.
• Scale horizontal axis (and labels) to fit the supplied tasks.
• Don't mutate dates; store temporal metadata in a Map somewhere.
• Auto-import and upgrade previous data format from URL.
• Add e2e tests.
• Re-consider @js-temporal/polyfill usage (it's pretty large; maybe check dayjs?)

View years example

View months example

View weeks example

View days example

[vercel]

This pull request is being automatically deployed with Vercel (learn more).
To see the status of your deployment, click below or on the icon next to each commit.

🔍 Inspect: https://vercel.com/bvaughn/planner/DLd9qPJFuT7cV3Xdf1m2PmRzKEV2
✅ Preview: https://planner-git-support-units-bvaughn.vercel.app

[bvaughn]

Seeing some e2e snapshot flakiness; reported via microsoft/playwright#11177