Add the Swift version for podspec

dreampiggy · dreampiggy · commit b1c2a99d08b7 · 2019-08-09T15:59:39.000+08:00
diff --git a/SDWebImageSwiftUI.podspec b/SDWebImageSwiftUI.podspec
@@ -30,4 +30,5 @@ Which aims to provide a better support for SwiftUI users.
 
   s.frameworks = 'SwiftUI'
   s.dependency 'SDWebImage', '~> 5.1'
+  s.swift_version = '5.0'
 end
