Can't use multiple names in a standalone kind signature
You can put multiple names in a single type signature, like so:
```hs
id1, id2 :: a -> a
id1 = id
id2 = id
```
However, the same does not hold for `StandaloneKindSignatures`. For example, the following program fails to parse:
```hs
{-# LANGUAGE StandaloneKindSignatures #-}
module Bug where
import Data.Kind
type T1, T2 :: Type -> Type
type T1 = Maybe
type T2 = Maybe
```
```
[1 of 1] Compiling Bug ( Bug.hs, Bug.o )
Bug.hs:6:8: error: parse error on input ‘,’
|
6 | type T1, T2 :: Type -> Type
| ^
```
This seems like it would be nice to have for consistency's sake.
issue