Added notices to constraint layout nuspec

Author: Redth

External-Dependency-Info.txt

@@ -7,10 +7,10 @@ notice and the license under which Microsoft received such third party
 material are set forth below.  Microsoft reserves all other rights not 
 expressly granted, whether by implication, estoppel or otherwise.
 
-########################################
-# Google Android Support libraries
+#########################################################
+# Google Android Support libraries and Constraint Layout
 # https://maven.google.com/
-########################################
+#########################################################
 
                                  Apache License
                            Version 2.0, January 2004

constraint-layout/nuget/Xamarin.Android.Support.Constraint.Layout.nuspec

@@ -18,5 +18,7 @@
   </metadata>
   <files>
     <file src="output/Xamarin.Android.Support.Constraint.Layout.dll" target="lib/MonoAndroid70" />
+
+    <file src="External-Dependency-Info.txt" target="THIRD-PARTY-NOTICES.txt" />
   </files>
 </package>