Allow writable `computed`s to be picked up by `mapWritableState`

[soetz]

What problem is this solving

At the moment, when attempting to use a writable computed (computed({ get () { … }, set (value) { … } })) with mapWritableState, TS reports an error. I assume that this is because mapWritableState, unlike mapState, only allows state and not computeds.

Despite TypeScript complaining, it seems like it does work as expected at runtime (but I did not test extensively).

https://play.pinia.vuejs.org/#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

Proposed solution

Allow computeds that are writable (WritableComputedRef) to be used within mapWritableState.

Describe alternatives you've considered

No response

[noootwo]

I'd like to do this, I will make a pull request next week.

It looks like it won 't start until the #2805 is merged.