[50] ensure multi-realm-scoped value in the nodeRequestScopedFeaturesStoreFactory export of the features package

[TomStrepsil]

Issue

resolves #50

Details

• Added a FeaturesStoreFactory interface, mandating that all features stores are created with a named toggleType
  • for the nodeRequestScopedFeaturesStoreFactory this is used to key the features store against a a runtime-wide global symbol to ensure it can be shared in cross-realm runtimes (e.g. NextJS). Hence, there can only be a single features store per named toggleType, for this store type. See express-http-context for similar.
  • this supplants the name property the reactContextFeaturesStoreFactory, required previously to provide a nice displayName for the react context provider. Its also used to form part of the id of the backing script for the ssrBackedReactContextFeaturesStoreFactory

Scout Rule

• Fix JSDoc output for interfaces
• Fixed descriptions in test files to better match name of factories
• Rename nodeRequestScopedStoreFactory to nodeRequestScopedFeaturesStoreFactory, for consistency
• Improve valtio examples in the README.md

Upgrade guide

This change will represent breaking changes in consumers of the features package.

Any use of stores now require a toggleType property, replacing the name that may have come before. It should represent the type of toggle, e.g. "experiments".

Any name import of nodeRequestScopedStoreFactory should now import nodeRequestScopedFeaturesStoreFactory

CheckList

• PR starts with [ISSUE_ID].
• Has been tested (where required) before merge to main.