Add `IDETemplateMacros.plist` to generate correct File Header

[fbernutz]

Resolves #53

This file is located under the example projects workspace (Example/AccessibilitySnapshot.xcworkspace/xcshareddata/), so it's shared with all developers working with the workspace. Tested this and Xcode now creates a new file with this content:

//
//  Copyright 2021 Square Inc.
//
//  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

To make it work I had to change the organization name of the workspace from CocoaPods to Square Inc..