Sucrase support

Is there any way how the hot loader could work directly with [sucrase](https://sucrase.io/)? Currently it requires the slow babel step to transpile typescript into es6 (https://github.com/alangpierce/sucrase/issues/228):

```
// Load TypeScript (.ts, .tsx).
{
test: /\.tsx?$/,
use: [
...(isDevServer
? [
{
loader: 'babel-loader',
options: {
babelrc: false,
plugins: ['react-hot-loader/babel'],
},
},
]
: []),
...(targetES6
? [
{
loader: '@sucrase/webpack-loader',
options: {
transforms: ['imports', 'jsx', 'typescript'],
},
},
]
: [{ loader: 'ts-loader', options: { configFile: paths.tsConfig } }]),
],
},
```

Start by tracing the TypeScript loader configuration shown in the issue and compare the babel-loader and @sucrase/webpack-loader paths. Done means the hot loader can work directly with Sucrase for TypeScript without requiring the slow Babel transpilation step.

Written by the indexing model from the issue text.