[typescript] Re-export Theme type in @material-ui/styles

• This is not a v0.x issue.
• I have searched the issues of this repository and believe that this is not a duplicate.

Context 🔦

Currently, to use makeStyles with Theme, I’ll have to use 2 imports:

import { makeStyles } from '@material-ui/styles';
import { Theme } from '@material-ui/core';

const useStyles = makeStyles((theme: Theme) => ({
  // ...
}));

I’d be great if I we can update the styles package so that it re-export the Theme type from core, because I tend to group similar components of material-ui into 1 import statement:

import { makeStyles, Theme } from '@material-ui/styles';

styles already uses Theme type from core, so I believe making a re-exports should not be a big problem.

Thank you.

[eps1lon]

We should just drop the breaking change. I can see no benefit and from my experience the whole @material-ui/styles vs. @material-ui/core/styles usage has only caused confusion.

I’m not sure some vaguely planned feature is a good reason to introduce a breaking change.

[eps1lon]

We should just re-export the ThemeProvider from @material-ui/styles in @material-ui/core/styles. At this point I don’t think we should actually advertise @material-ui/styles if people are using @material-ui/core. At least I don’t see the benefit of importing from @material-ui/styles. If there is one we should document it.