feat: add shortcut for Form's validateOn params

Author: r13v

EffectorForms/Set+ValidationEvent.swift

@@ -0,0 +1,7 @@
+extension Set where Element == ValidationEvent {
+    static let all = Set(ValidationEvent.allCases)
+
+    static let submit = Set([ValidationEvent.submit])
+    static let change = Set([ValidationEvent.change])
+    static let blue = Set([ValidationEvent.blur])
+}

EffectorForms/Validator.swift

@@ -1,7 +1,9 @@
 import Foundation
 
-public enum ValidationEvent {
-    case submit, blur, change
+public enum ValidationEvent: CaseIterable {
+    case submit
+    case blur
+    case change
 }
 
 public struct ValidationError<Value: Equatable>: Equatable {