Add icon and use licence expression for NuGet.

Unlike framework, if other components are packed, they are likely to use different icons.

Directory.Build.props

@@ -21,7 +21,7 @@
   </PropertyGroup>
   <PropertyGroup Label="Nuget">
     <Authors>ppy Pty Ltd</Authors>
-    <PackageLicenseUrl>https://github.com/ppy/osu/blob/master/LICENCE.md</PackageLicenseUrl>
+    <PackageLicenseExpression>MIT</PackageLicenseExpression>
     <PackageProjectUrl>https://github.com/ppy/osu</PackageProjectUrl>
     <RepositoryUrl>https://github.com/ppy/osu</RepositoryUrl>
     <PackageReleaseNotes>Automated release.</PackageReleaseNotes>

osu.Game/osu.Game.csproj

@@ -7,7 +7,14 @@
   <PropertyGroup Label="Nuget">
     <Title>osu!</Title>
     <PackageId>ppy.osu.Game</PackageId>
+    <PackageIcon>icon.png</PackageIcon>
   </PropertyGroup>
+  <ItemGroup Label="Icon">
+    <None Include="..\assets\lazer-nuget.png">
+      <Pack>True</Pack>
+      <PackagePath>icon.png</PackagePath>
+    </None>
+  </ItemGroup>
   <ItemGroup Label="Package References">
     <PackageReference Include="Humanizer" Version="2.7.9" />
     <PackageReference Include="Microsoft.EntityFrameworkCore.Sqlite" Version="2.2.6" />