Add support for Umbraco 11

[rickbutterfield]

The below error appears when trying to use this package with Umbraco 11:

System.MissingMethodException: Method not found: 'Void Umbraco.Extensions.ServiceCollectionExtensions.AddUnique(Microsoft.Extensions.DependencyInjection.IServiceCollection)'.
   at Our.Umbraco.PersonalisationGroups.Core.ServicesConfiguration.AddProviders(IServiceCollection services, IConfigurationSection configSection)
   at Our.Umbraco.PersonalisationGroups.Core.ServicesConfiguration.AddPersonalisationGroups(IUmbracoBuilder builder, IConfiguration config)

AddUnique requires both a TService and TImplementing in Umbraco 11, so I believe switching this to AddSingleton should resolve the issue?

[AndyButland]

Thanks @rickbutterfield - I had planned some time over the holidays to check this package worked OK on 11. Thanks for answering it for me and fixing it! Does look like this will work on 10 too so it'll just be a case of releasing a patch that'll then work on both versions.

[AndyButland]

I've released 3.2.3 now with this update. Thanks again and Merry Christmas!