[LayoutSpecExamples] Added swift counterpart. (#2576)

* [LayoutSpecExamples] Added swift counterpart.

* Fixed copyright text.

examples/LayoutSpecExamples-Swift/Sample/OverviewCellNode.swift

@@ -0,0 +1,46 @@
+//
+//  OverviewCellNode.swift
+//  Sample
+//
+//  Copyright (c) 2014-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under the BSD-style license found in the
+//  LICENSE file in the root directory of this source tree. An additional grant
+//  of patent rights can be found in the PATENTS file in the same directory.
+//
+//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+//  FACEBOOK BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+//  ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+//  CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+//
+
+import AsyncDisplayKit
+
+class OverviewCellNode: ASCellNode {
+
+  let layoutExampleType: LayoutExampleNode.Type
+
+  fileprivate let titleNode = ASTextNode()
+  fileprivate let descriptionNode = ASTextNode()
+
+  init(layoutExampleType le: LayoutExampleNode.Type) {
+    layoutExampleType = le
+
+    super.init()
+    self.automaticallyManagesSubnodes = true
+
+    titleNode.attributedText = NSAttributedString.attributedString(string: layoutExampleType.title(), fontSize: 16, color: .black)
+    descriptionNode.attributedText = NSAttributedString.attributedString(string: layoutExampleType.descriptionTitle(), fontSize: 12, color: .lightGray)
+  }
+
+  override func layoutSpecThatFits(_ constrainedSize: ASSizeRange) -> ASLayoutSpec {
+    let verticalStackSpec = ASStackLayoutSpec.vertical()
+    verticalStackSpec.alignItems = .start
+    verticalStackSpec.spacing = 5.0
+    verticalStackSpec.children = [titleNode, descriptionNode]
+
+    return ASInsetLayoutSpec(insets: UIEdgeInsets(top: 10, left: 16, bottom: 10, right: 10), child: verticalStackSpec)
+  }
+
+}