Investigate replacing cssInjectedByJsPlugin?

[joelvdavies]

It will not be compatible with ESM if we move to it in the future. For context this was added to get uppy styles to import when loading in scigateway, so removing it from the build breaks it. Manually adding a works correctly.

Potential useful info includes:

• vite-plugin-single-spa (which has ways of auto loading css)
• https://webjose.hashnode.dev/injecting-micro-frontend-css-in-single-spa

Likely requires SciGateway changes to single-spa.