Require watchOS 3 consistently

Fixed an issue where the readme claimed watchOS 2 was supported while the SPM configuration required watchOS 4 by splitting the difference (and aligning with the Xcode project and CocoaPods podspec).

Author: 1ec5

Package.swift

@@ -6,7 +6,7 @@ import PackageDescription
 let package = Package(
     name: "MapboxDirections",
     platforms: [
-        .macOS(.v10_12), .iOS(.v10), .watchOS(.v4), .tvOS(.v12)
+        .macOS(.v10_12), .iOS(.v10), .watchOS(.v3), .tvOS(.v12)
     ],
     products: [
         // Products define the executables and libraries produced by a package, and make them visible to other packages.

README.md

@@ -54,7 +54,7 @@ This repository contains an example application that demonstrates how to use the
    * iOS 10.0 or above
    * macOS 10.12.0 or above
    * tvOS 10.0 or above
-   * watchOS 2.0 or above
+   * watchOS 3.0 or above
    * Any Linux distribution supported by Swift
 
 v0.30.0 is the last release of MapboxDirections.swift that supports a minimum deployment target of iOS 9._x_, macOS 10.11._x_, tvOS 9._x_, or watchOS 2._x_. v0.30.0 is also the last release that is compatible with Objective-C or AppleScript code.