Add common usage scenario.

README.md

@@ -2,6 +2,10 @@
 
 Awaits already in-flight calls and their value.
 
+A common application is when concurrent calls require authentication secrets which are expired and should only be
+refreshed one at a time. This acts as a queue for the result if another thread of execution already started the network
+request.
+
 ## Usage
 
 For each call that should only be executed one at a time, create a new instace of `InFlightValueProvider`:
@@ -23,7 +27,7 @@ original call. Once the value has been returned to all waiting threads, the prov
 
 ## Installation
 
-Using the Swift Package Manager, add this line to your `Package.swift`:
+Using the Swift Package Manager, add this line to your `Package.swift` as a dependency:
 
 ```swift
     .package(url: "https://github.com/sgade/InFlightValue", from: "1.0.0"),