Bump WorkflowSwiftUIExperimental to 0.4 (#274)

Author: mjohnson12

WorkflowSwiftUIExperimental.podspec

@@ -2,7 +2,7 @@ require_relative('version')
 
 Pod::Spec.new do |s|
     s.name         = 'WorkflowSwiftUIExperimental'
-    s.version      = '0.3'
+    s.version      = '0.4'
     s.summary      = 'Infrastructure for Workflow-powered SwiftUI'
     s.homepage     = 'https://www.github.com/square/workflow-swift'
     s.license      = 'Apache License, Version 2.0'