Correct imports when imported in certain setups.

[akademy]

I'm seeing several import errors when adding the component via npmjs in an existing project.

Errors are similar to:

ERROR in ./node_modules/@diamondlightsource/sci-react-ui/dist/index.esm.js 6:0-36
Module not found: Error: Can't resolve '@mui/material/Grid2' in '.../frontend/node_modules/@diamondlightsource/sci-react-ui/dist'
Did you mean 'index.js'?
BREAKING CHANGE: The request '@mui/material/Grid2' failed to resolve only because it was resolved as fully specified (probably because the origin is strict EcmaScript Module, e. g. a module with javascript mimetype, a '.mjs' file, or a '.js' file where the package.json contains '"type": "module"').
The extension in the request is mandatory for it to be fully specified.
Add the extension to the request.

These changes fix this error, but wonder if this isn't a build problem...?!