Upgrade Storybook and Vite

[axelboc]

Storybook 7.5

• support for Vite 5
• old stories format now deprecated

Storybook 7.6

• faster start-up times with react-docgen (enabled with config)
• storybook doctor command to debug setup issues (added to CONTRIBUTING guide)
• last minor before v8

Vite 5 + Rollup 4

• Node 18+
• CJS API now deprecated
  • Had to add type: "module" to the demo's package.json and rename .eslintrc.js to .eslintrc.cjs
  • There's the same warning in Storybook but this fix doesn't make it go away (but it doesn't hurt, so I've done it anyway).
• fixes a bunch of subtle inconsistencies between dev and build
• CLI shortcut keys now require pressing the Enter key, so I'm re-enabling open: true
• migration guide
• new performance guide to troubleshoot slow start/build/hmr