Added createFacetContext

[Shenato]

This PR adds a new facet function createFacetContext

Which can be used to create a context that holds a facet with the type Facet instead of WritableFacet.

NOTE: Writable facets you provide into the context provider are still technically writable as you can call them with .set() however the function will change the type to show that the facet doesn't have a setter internally (in reality it does).

This hopefully will help steer consumers away from setting facets arbitrarily using createFacet and facet.set() instead of sticking to more conventional react methods and or useFacetX hooks

this turns code like this

const myFancyContext = createContext<Facet<number | undefined>>(createFacet({ initialValue: undefined }))
export const useMyFancyContext = () => useContext(myFancyContext)

into

const myFancyContext = createFacetContext<number | undefined>(undefined)
export const useMyFancyContext = () => useContext(myFancyContext)

In the first instance the Facet was a WritableFacet and was gonna stay that way no matter what, in the 2nd instance it is no longer a WritableFacet, which hopefully should offer a cleaner method of writing a context holding a facet for it's property of not triggering reconciliation and not for it's property of being a writable store of value.

[pirelenito]

Awesome stuff! 👏