Add 3rd party licenses

Directory.Build.props

@@ -12,6 +12,8 @@
     <Company>Microsoft</Company>
     <Product>Xamarin.Forms</Product>
     <ProduceReferenceAssembly Condition="'$(UsingMicrosoftNETSdk)' == 'True' AND '$(Configuration)' == 'Debug'">True</ProduceReferenceAssembly>
+    <LicenseFile>$(MSBuildThisFileDirectory)LICENSE</LicenseFile>
+    <PackageThirdPartyNoticesFile>$(MSBuildThisFileDirectory)THIRD-PARTY-NOTICES.TXT</PackageThirdPartyNoticesFile>
   </PropertyGroup>
   <PropertyGroup>
     <GitDefaultBranch>main</GitDefaultBranch>

Nuget.targets

@@ -13,4 +13,14 @@
     <PackageReference Include="Xamarin.Forms.AppLinks" Version="$(XamarinFormsVersion)">
     </PackageReference>
   </ItemGroup>
+
+  <!-- License files -->
+  <ItemGroup>
+    <None Include="$(LicenseFile)"
+          PackagePath="$([System.IO.Path]::GetFileName('$(LicenseFile)'))"
+          Pack="true" />
+    <None Include="$(PackageThirdPartyNoticesFile)"
+          PackagePath="$([System.IO.Path]::GetFileName('$(PackageThirdPartyNoticesFile)'))"
+          Pack="true" />
+  </ItemGroup>
 </Project>