docs: update usage and installation

Author: longinius

README.md

@@ -1,6 +1,8 @@
 # Swift ISO 8601 Duration
 
+![](https://img.shields.io/badge/Swift-5.5-orange?style=flat&color=F05138)
 ![](https://img.shields.io/badge/Swift%20Package%20Manager-compatible-orange?style=flat&color=F05138)
+![](https://img.shields.io/badge/Platform-iOS%20macOS%20tvOS%20watchOS-green?style=flat)
 
 An ISO 8601 Duration parser for Swift. Inspired by the [Luxon](https://moment.github.io/luxon) duration object.
 
@@ -15,18 +17,21 @@ An ISO 8601 Duration parser for Swift. Inspired by the [Luxon](https://moment.gi
 
 ## Usage
 
+Create a duration from an ISO 8601 string.
 ```swift
-let duration = Duration(fromIso: "P2Y4M12DT5H34M48S")
+let duration = Duration(fromISO: "P2Y4M12DT5H34M48S")
 
 // Duration contains the parsed values
-duration.years // 2
-duration.months // 4
-duration.days // 12
-duration.hours // 5
-duration.minutes // 34
-duration.seconds // 48
-
-// Create `DateComponents` object from `Duration`
+duration.year // 2
+duration.month // 4
+duration.day // 12
+duration.hour // 5
+duration.minute // 34
+duration.second // 48
+```
+
+Get a `DateComponents` object from duration.
+```swift
 let dateComponents = duration.dateComponents
 ```
 
@@ -35,7 +40,9 @@ let dateComponents = duration.dateComponents
 
 The [Swift Package Manager](https://www.swift.org/package-manager/) is a tool for managing the distribution of Swift Code. It's integrated into the `swift` compiler. 
 
-To use `Duration`, simply add the following Package as dependency:
-```
-https://github.com/longinius/duration.git
+To use `Duration` in your project, simply add this Package as dependency:
+```swift
+dependencies: [
+    .package(url: "https://github.com/longinius/duration.git", .upToNextMajor(from: "1.0.0"))
+]
 ```