Add compatibility testing for Framework 6.1

Closes gh-905

spring-restdocs-webtestclient/build.gradle

@@ -21,3 +21,10 @@ dependencies {
 
 	testRuntimeOnly("org.springframework:spring-context")
 }
+
+compatibilityTest {
+	dependency("Spring Framework") { springFramework ->
+		springFramework.groupId = "org.springframework"
+		springFramework.versions = ["6.1.+"]
+	}
+}