Add condensed readme to package

Author: smoogipoo

README_nuget.md

@@ -0,0 +1,17 @@
+C# bindings for the [SDL3](https://github.com/libsdl-org/SDL) family of libraries.
+
+| Product                                                          | Usage                                  | Package                                                                                                                    |
+|------------------------------------------------------------------|----------------------------------------|----------------------------------------------------------------------------------------------------------------------------|
+| [`SDL`](https://github.com/libsdl-org/SDL/tree/main)             | `dotnet add package ppy.SDL3-CS`       | [![NuGet](https://img.shields.io/nuget/v/ppy.SDL3-CS?label=nuget)](https://www.nuget.org/packages/ppy.SDL3-CS)             |     
+| [`SDL_image`](https://github.com/libsdl-org/SDL_image/tree/main) | `dotnet add package ppy.SDL3_image-CS` | [![NuGet](https://img.shields.io/nuget/v/ppy.SDL3_image-CS?label=nuget)](https://www.nuget.org/packages/ppy.SDL3_image-CS) | 
+| [`SDL_ttf`](https://github.com/libsdl-org/SDL_ttf/tree/main)     | `dotnet add package ppy.SDL3_ttf-CS`   | [![NuGet](https://img.shields.io/nuget/v/ppy.SDL3_ttf-CS?label=nuget)](https://www.nuget.org/packages/ppy.SDL3_ttf-CS)     |     
+
+Contributions to keep the bindings up-to-date with upstream changes are welcome. If you have improvements or updates, feel free to submit a pull request.
+
+## Platform support
+
+| Product         | `win-x64` | `win-x86` | `win-arm64` | `osx-arm64` | `osx-x64` | `linux-x64` | `linux-x86` | `linux-arm64` | `linux-arm` | `ios`   | `android` |
+|-----------------|-----------|-----------|-------------|-------------|-----------|-------------|-------------|---------------|-------------|---------|-----------|
+| `SDL3-CS`       | ✓   | ✓   | ✓     | ✓     | ✓   | ✓     | ✓     | ✓       | ✓     | ✓ | ✓   |
+| `SDL3_image-CS` | ✓   | ✓   | ✓     | ✓     | ✓   | ✓     | ✓     | ✓       | ✓     |         |           |
+| `SDL3_ttf-CS`   | ✓   | ✓   | ✓     | ✓     | ✓   | ✓     | ✓     | ✓       | ✓     |         |           |

SDL3-CS/SDL3-CS.csproj

@@ -19,9 +19,14 @@
     <PackageReleaseNotes>Automated release.</PackageReleaseNotes>
     <PackageLicenseExpression>MIT</PackageLicenseExpression>
     <PackageProjectUrl>https://github.com/ppy/SDL3-CS</PackageProjectUrl>
+    <PackageReadmeFile>README_nuget.md</PackageReadmeFile>
     <RepositoryUrl>https://github.com/ppy/SDL3-CS</RepositoryUrl>
   </PropertyGroup>
 
+  <ItemGroup>
+    <None Include="$(MSBuildThisFileDirectory)..\README_nuget.md" Pack="true" PackagePath="\"/>
+  </ItemGroup>
+
   <ItemGroup>
     <ProjectReference Include="..\SDL3-CS.SourceGeneration\SDL3-CS.SourceGeneration.csproj" OutputItemType="Analyzer" ReferenceOutputAssembly="false"/>
   </ItemGroup>

SDL3_image-CS/SDL3_image-CS.csproj

@@ -17,9 +17,14 @@
     <PackageReleaseNotes>Automated release.</PackageReleaseNotes>
     <PackageLicenseExpression>MIT</PackageLicenseExpression>
     <PackageProjectUrl>https://github.com/ppy/SDL3-CS</PackageProjectUrl>
+    <PackageReadmeFile>README_nuget.md</PackageReadmeFile>
     <RepositoryUrl>https://github.com/ppy/SDL3-CS</RepositoryUrl>
   </PropertyGroup>
 
+  <ItemGroup>
+    <None Include="$(MSBuildThisFileDirectory)..\README_nuget.md" Pack="true" PackagePath="\"/>
+  </ItemGroup>
+
   <ItemGroup>
     <ProjectReference Include="..\SDL3-CS.SourceGeneration\SDL3-CS.SourceGeneration.csproj" OutputItemType="Analyzer" ReferenceOutputAssembly="false"/>
     <ProjectReference Include="..\SDL3-CS\SDL3-CS.csproj"/>

SDL3_ttf-CS/SDL3_ttf-CS.csproj

@@ -17,9 +17,14 @@
     <PackageReleaseNotes>Automated release.</PackageReleaseNotes>
     <PackageLicenseExpression>MIT</PackageLicenseExpression>
     <PackageProjectUrl>https://github.com/ppy/SDL3-CS</PackageProjectUrl>
+    <PackageReadmeFile>README_nuget.md</PackageReadmeFile>
     <RepositoryUrl>https://github.com/ppy/SDL3-CS</RepositoryUrl>
   </PropertyGroup>
 
+  <ItemGroup>
+    <None Include="$(MSBuildThisFileDirectory)..\README_nuget.md" Pack="true" PackagePath="\"/>
+  </ItemGroup>
+
   <ItemGroup>
     <ProjectReference Include="..\SDL3-CS.SourceGeneration\SDL3-CS.SourceGeneration.csproj" OutputItemType="Analyzer" ReferenceOutputAssembly="false"/>
     <ProjectReference Include="..\SDL3-CS\SDL3-CS.csproj"/>