refactor(core): rename core pkg dir to core

packages/core/src/store/index.ts

@@ -0,0 +1,4 @@
+export { default as useHooks, createHooks } from './hooks'
+export { default as useActions } from './actions'
+export { default as useState, defaultEdgeTypes, defaultNodeTypes } from './state'
+export { default as useGetters } from './getters'