splitVendorChunkPlugin is deprecated

[sandbergja]

What maintenance needs to be done?

Replace splitVendorChunkPlugin, which is used in our vite.config.js, with a supported option. The deprecation message says "use build.rollupOutput.manualChunks or framework specific configuration"

Level of urgency

• High
• Moderate
• Low

Why is this maintenance needed?

Our build process should not rely on deprecated plugins, or we risk getting stuck on an old version

Acceptance criteria

• We no longer use splitVendorChunkPlugin