Type-safe reducers with @reduxjs/toolkit

[kesslern]

Redux reducer enhancements:

• Use createSlice from @reduxjs/toolkit to create type-safe reducers and auto-generate action creators.
• This also enhances the reduces with immerjs, allowing state to be "mutated" inside reducers.

Type improvements:

• Use type-safe thunk definitions
• Convert loginToJellyfin API function to a thunk for consistency
• Use auto-generated RootState type for Redux state type
• Add custom useSelector hook that uses RootState for type-safety
• Remove global JellyfinProps type

Build improvements:

• Add standard and standard-jsx eslint rules
• Update type definitions in package.json and move them all to dev dependencies section

Store persistence updates:

• Update to latest version of redux-persist
• Ignore redux-persist actions when checking for state serializability
• Add persistence callback to re-initialize the API client with any available data