Update README.md

Author: yimajo

README.md

@@ -59,7 +59,10 @@ https://github.com/CuriositySoftware/swift-fatal-test-value
 If you are using Package.swift add:
 
 ```swift
-.package(url: "https://github.com/CuriositySoftware/swift-fatal-test-value/", from: "1.0.0")
+.package(
+    url: "https://github.com/CuriositySoftware/swift-fatal-test-value/",
+    .upToNextMajor(from: "1.0.0")
+)
 ```
 
 and then add the product to any target that needs access to the macro: