Avoid importing `editor.css` twice (#2373)

This PR prevents importing `editor.css` twice. Looks like we currently
import all the css files for all the routes in the examples app. This
means that we were importing both `tldraw.css` (which includes
`editor.css`) as well as `editor.css` directly (this last one we
imported from `OnlyEditor.tsx`).

This caused all the classes to be defined twice and it made it harder to
debug things - you might have disabled the styles in one of the
definitions but you didn't see any changes because the other definitions
still applied.


![image](https://github.com/tldraw/tldraw/assets/2523721/8d84a145-bfc6-49c1-af44-7f456510b884)

I don't think importing `editor.css` is needed as we do import the full
`tldraw.css` anyway.


![image](https://github.com/tldraw/tldraw/assets/2523721/ccc22af5-1c3a-4ac4-b24e-ee3959c99d3c)


### Change Type

- [x] `patch` — Bug fix
- [ ] `minor` — New feature
- [ ] `major` — Breaking change
- [ ] `dependencies` — Changes to package dependencies[^1]
- [ ] `documentation` — Changes to the documentation only[^2]
- [ ] `tests` — Changes to any test code only[^2]
- [ ] `internal` — Any other changes that don't affect the published
package[^2]
- [ ] I don't know

[^1]: publishes a `patch` release, for devDependencies use `internal`
[^2]: will not publish a new version

### Release Notes

- Prevent importing `editor.css` twice which should help when debugging
the styles via developer console.

apps/examples/src/examples/only-editor/OnlyEditor.tsx

@@ -1,7 +1,6 @@
 /* eslint-disable import/no-extraneous-dependencies */
 
 import { Editor, PositionedOnCanvas, TldrawEditor, createShapeId, track } from '@tldraw/editor'
-import '@tldraw/editor/editor.css'
 import { MiniBoxShapeUtil } from './MiniBoxShape'
 import { MiniSelectTool } from './MiniSelectTool'