Extract svelte/stores into a separate library

[btakita]

Svelte Stores are a powerful observable container "cell" library which is unique in the Store ecosystem. Even though Svelte Stores can be used without the components, it would be useful for Svelte Stores to be extracted into a separate library so people who are not familiar with Svelte are more inclined to consider Svelte Stores as an option.

Another benefit of making svelte/stores a distinct library is that it would be easier to create an ecosystem around svelte/stores.

[btakita]

See holochain/syn#21

[Conduitry]

This has come up before in #3567 and I think the answer is the same. If someone wants to automatically publish this, they are free to.