Swap of key and type in custom store

[stephane]

I was surprised by the inversion of type and key in custom store of Svelvet.
We have many TS types such as:

• Map<CustomEdgeKey, WritableEdge>
• Record<string, Writable<unknown> | Readable<unknown>>

but the Svelvet's Store interface is defined in the opposite way export interface Store<T, K>.
IMHO it generates disturbing usage and definitions such as:

export interface Store<T, K> {
	subscribe: Writable<Map<K, T>>['subscribe'];
        ...

where T, V is swapped to K, V.

I propose to use common K, V ordering.