feat: Add SourceLink and push symbols to NuGet.org (#825)

Co-authored-by: RomainHautefeuille: #806

Create and publish symbol packages (.snupkg) with Source Link.
Source Link documentation:
https://devblogs.microsoft.com/dotnet/producing-packages-with-source-link/
https://github.com/dotnet/sourcelink

ContinuousIntegrationBuild is set during CI to avoid linking to paths
from build vm, but not when built manually where local paths are relevant.

Author: sbellone

src/Algolia.Search/Algolia.Search.csproj

@@ -23,8 +23,15 @@
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
     <TargetFrameworks>netstandard2.1;netstandard2.0;netstandard1.3</TargetFrameworks>
     <LangVersion>7.3</LangVersion>
+    <IncludeSymbols>true</IncludeSymbols>
+    <SymbolPackageFormat>snupkg</SymbolPackageFormat>
+    <PublishRepositoryUrl>true</PublishRepositoryUrl>
   </PropertyGroup>
   <ItemGroup>
+    <PackageReference Include="Microsoft.SourceLink.GitHub" Version="1.1.1">
+      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
+      <PrivateAssets>all</PrivateAssets>
+    </PackageReference>
     <PackageReference Include="Newtonsoft.Json" Version="13.0.1" />
     <None Include="images\icon.png" Pack="true" PackagePath="\" />
   </ItemGroup>

src/Directory.Build.props

@@ -0,0 +1,5 @@
+<Project>
+  <PropertyGroup Condition="'$(CI)' == 'true'">
+    <ContinuousIntegrationBuild>true</ContinuousIntegrationBuild>
+  </PropertyGroup>
+</Project>