Adds missing documentation for the Store initializer (pointfreeco#1940)

* Add missing `Store` initializer documentation

* Update Sources/ComposableArchitecture/Store.swift

* Update and rename Store.swift to Store.swift

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Co-authored-by: Brandon Williams <[email protected]>

Author: kristofferjohansson

Sources/ComposableArchitecture/Store.swift

@@ -141,6 +141,8 @@ public final class Store<State, Action> {
   /// - Parameters:
   ///   - initialState: The state to start the application in.
   ///   - reducer: The reducer that powers the business logic of the application.
+  ///   - prepareDependencies: A closure that can be used to override dependencies that will be accessed 
+  ///     by the reducer.
   public convenience init<R: ReducerProtocol>(
     initialState: @autoclosure () -> R.State,
     reducer: R,