Add note to mention Mediator and MediatR

Use docs site as project URL

Don't validate public API in package publishing

Since we want the analyzers for tracking shipped APIs, not to prevent innovation such as adding ExecuteStream for .net6.0+ targets.

Fix image links in readmes for display in nuget.org

Add note on observable producers

Fix automapper dependency

If we don't specify the target framework, the packaging project will just take a dependency with no framework. This doesn't work when we *also* have framework-specific dependencies, and will cause the dependency to be lost entirely when nuget performs a restore.

In other words, if you have non-framework specific dependencies AND framework specific dependencies, you will only get the latter in the restore graph.

Add public api analyzers to avoid inadvertent breaking changes

Add command and event payloads to activity

By exposing these as custom properties, we allow listeners to perform additional operations on them without having to extend the message bus itself.

Bump Microsoft.Build.NoTargets from 3.6.0 to 3.7.0

Bumps [Microsoft.Build.NoTargets](https://github.com/Microsoft/MSBuildSdks) from 3.6.0 to 3.7.0.
- [Release notes](https://github.com/Microsoft/MSBuildSdks/releases)
- [Changelog](https://github.com/microsoft/MSBuildSdks/blob/main/RELEASE.md)
- [Commits](microsoft/MSBuildSdks@Microsoft.Build.NoTargets.3.6.0...Microsoft.Build.NoTargets.3.7.0)

---
updated-dependencies:
- dependency-name: Microsoft.Build.NoTargets
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Set activity status to error when an exception is recorded

Fixes #77