Finally publishing the v2.0 release.

• Configure Mediator through AddMediator call (assembly attribute still works) (https://github.com/martinothamar/Mediator/pull/21, https://github.com/martinothamar/Mediator/pull/24)
• Throw ArgumentNullException for null messages (https://github.com/martinothamar/Mediator/pull/22)
• Pass Publish<INotification> calls to Publish(object) (https://github.com/martinothamar/Mediator/pull/22)
• Optimize notifications (52ns -> 11ns for the most common case) (https://github.com/martinothamar/Mediator/pull/23)
• Cleanup and optimization in source generator (https://github.com/martinothamar/Mediator/pull/25, thanks @Timmoth!)
• Modernize source generator to support both 3.8 and 4.0 Roslyn versions (also prepare for incremental codegen) (https://github.com/martinothamar/Mediator/pull/26)
• Updated benchmarks to account for changes (https://github.com/martinothamar/Mediator/pull/27)
• Smoketests, unittests, memory allocation tests (https://github.com/martinothamar/Mediator/pull/28, https://github.com/martinothamar/Mediator/pull/29)
• Cleanup analysis-part of source generator, use 6.0.0 of .NET references (https://github.com/martinothamar/Mediator/pull/30)
• Use csharpier for consistent formatting (https://github.com/martinothamar/Mediator/pull/31)
• Benchmark for source generation process (https://github.com/martinothamar/Mediator/pull/32)
• Bugfix for using arrays as response types (https://github.com/martinothamar/Mediator/issues/33, https://github.com/martinothamar/Mediator/pull/34)
• Multiple bugfixes for stream requests and structs (see linked PRs https://github.com/martinothamar/Mediator/issues/36, thanks @Tornhoof!)
• Improve error handling in source generation process (https://github.com/martinothamar/Mediator/issues/33#issuecomment-1146689609, https://github.com/martinothamar/Mediator/pull/40)
• Support Notification Handler Identification via Reflection (https://github.com/martinothamar/Mediator/issues/39, https://github.com/martinothamar/Mediator/pull/42, thanks @Tornhoof!)
• Fix defensive copy for non-readonly structs (https://github.com/martinothamar/Mediator/issues/43, https://github.com/martinothamar/Mediator/pull/44, thanks @Tornhoof!)
• Add missing debugger attributes (https://github.com/martinothamar/Mediator/pull/46)
• Bugfixes and benchmark for larger projects (https://github.com/martinothamar/Mediator/pull/41)
• Fix thread safety issue in ISourceGenerator/IIncrementalGenerator implementations (#56, thanks for reporting @AlexDelepine!)
• Typo fix in README (#61, thanks @sjmdsky!)