Allow returning NotStarted from GetWorkStatus

[hendrikdevloed]

Description

Please include a summary of problem/issue this pull request solves/accomplishes.

Fixes #56

Type of Change

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• Bug fix
• New Feature
• Documentation
• Code improvement
• Breaking change - if a public API changes, or any change that DOES or MAY require a major revision to the NuGet package version due to semver.
• Unit tests
• Code samples
• Added your repository URL to the readme because you make use of this super cool package! ;)
• Other

Please describe if other

Describe testing that was performed for your change

Remove section if not applicable

Checklist

• Read the https://github.com/OrleansContrib/Orleans.SyncWork/blob/main/CONTRIBUTING.md
• Ran unit tests and ensured they passed
• Added unit tests where applicable
• Referenced an issue where applicable
• Ran dotnet-format locally

[Kritner]

lgtm, thanks!

I'll probably try to get a new nuget package built and deployed within the next day or two