This moves the babel and postcss configs into the webpack config for ease of maintenance (and because we need variations of them). The typescript config is left outside the webpack config for IDEs to pick it up.
This reverts commit 7b89893645.
7b89893645
See https://github.com/matrix-org/matrix-react-sdk/pull/3292 Like react-sdk#3292, this fixes the couple source files which mix imports and module exports (they can't be mixed anymore).