plugin: add SourceLink support

Author: JohnTheGr8

Flow.Launcher.Plugin/Flow.Launcher.Plugin.csproj

@@ -27,6 +27,7 @@
     <PackageDescription>Reference this library if you want to develop a Flow Launcher plugin</PackageDescription>
     <PackageTags>flowlauncher</PackageTags>
     <GeneratePackageOnBuild>true</GeneratePackageOnBuild>
+    <PublishRepositoryUrl>true</PublishRepositoryUrl>
   </PropertyGroup>
 
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
@@ -68,6 +69,7 @@
   </ItemGroup>
 
   <ItemGroup>
+    <PackageReference Include="Microsoft.SourceLink.GitHub" Version="1.0.0" PrivateAssets="All"/>
     <PackageReference Include="JetBrains.Annotations" Version="2019.1.3" />
     <PackageReference Include="Mono.Cecil" Version="0.11.2" />
     <PackageReference Include="Newtonsoft.Json" Version="12.0.3" />