Add license header template and ignore file

Author: shahmishal

.license_header_template

@@ -0,0 +1,11 @@
+@@===----------------------------------------------------------------------===@@
+@@
+@@ This source file is part of the Swift open source project
+@@
+@@ Copyright (c) YEARS Apple Inc. and the Swift project authors
+@@ Licensed under Apache License v2.0 with Runtime Library Exception
+@@
+@@ See http://swift.org/LICENSE.txt for license information
+@@ See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+@@
+@@===----------------------------------------------------------------------===@@

.licenseignore

@@ -0,0 +1,10 @@
+**/*.mlmodel
+**/*.pbxproj
+**/*.png
+**/*.xcworkspacedata
+**/Package.swift
+.dir-locals.el
+.editorconfig
+.swift-version
+CODEOWNERS
+Package.swift