New rule: store callbacks must use set param

[tivac]

Description

Every now and then I forget how to properly use the "callback on subscriber" form of the built-in svelte stores, and end up writing something like this:

const store = writable(false, () => api.getData());

which doesn't work, because it should actually be written like this:

const store = writable(false, (set) => set(api.getData()));

Svelte REPL Example

A rule that ensures any readable or writable stores that use the callback form follow these rules would be great:

1. Callback must accept a single parameter
2. Somewhere within the callback function body it should execute that parameter as a function

I don't think we can get too much more descriptive about it, but even just those two checks would save me from debugging my bad stores.