Add a simple screen SwiftUI template.

RiotSwiftUI/Modules/Template/SimpleScreenExample/TemplateSimpleScreenViewModelProtocol.swift

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+// 
+// Copyright 2021 New Vector Ltd
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+import Foundation
+
+protocol TemplateSimpleScreenViewModelProtocol {
+    
+    var completion: ((TemplateSimpleScreenViewModelResult) -> Void)? { get set }
+    @available(iOS 14, *)
+    var context: TemplateSimpleScreenViewModelType.Context { get }
+}