fix: avoid duplicate symbol package publish

ci: publish package from github release

feat: production harden packaging and mediator registration

Merge branch 'main' of https://github.com/NastMz/SimpleMediator

refactor: Replace FluentAssertions with Shouldly in tests and update project URLs

Update Nast.SimpleMediator.nuspec

Delete Nast.SimpleMediator/PUBLISHING.md

fix: Remove PackageReleaseNotes from project file

fix: Update package version to 1.0.2 and include README in package

fix: Update restore and build commands to use solution path in NuGet publish workflow

fix: Improve null handling in service registration and update build commands in CI workflow

feat: Add test project for SimpleMediator and update dependencies

Add comprehensive unit tests and test infrastructure for SimpleMediator

feat: Enhance NuGet publishing workflow with API key verification and improved logging

feat: Add initial NuGet package configuration, build scripts, and publishing guide