Review and improve the structure of Context files

[jamcry]

From @edizcelik :

By the way, we can update the file structure here. We recently started using this convention on Tinyman and it looks quite nice:

.../ToastContext.tsx     <- this includes Contexts and the ToastContextProvider
.../ToastContext.utils.ts      <-  this includes the custom hooks for the consumers
.../ToastContext.reducer.ts      <- includes the reducer and the state stuff
.../ToastContext.constants.ts    <- includes constants related to the Context
.../ToastContext.types.ts      <- includes types related to the Context (if any)

Originally posted by @edizcelik in #197 (comment)

We can do this for Toast and Toggle contexts