Add System.Collections.Immutable

Signed-off-by: Xen <lordofxen@deskasoft.com>

Author: LordOfXen

HashifyNet/HashifyNet.csproj

@@ -66,6 +66,7 @@
   </PropertyGroup>
 
   <ItemGroup>
+    <PackageReference Include="System.Collections.Immutable" Version="9.0.8" />
     <PackageReference Include="System.IO.Hashing" Version="9.0.8" />
     <PackageReference Include="System.Memory" Version="4.6.3" />
   </ItemGroup>
@@ -110,3 +111,4 @@
 
 
 
+