Move ColorToolViewModel to shared project

[JLdgu]

Both changes are to Demo projects

[Keboo]

Hey @JLdgu, while reviewing your PR, I'd suggest the following code changes:

👉 Code Suggestion for #3624

https://github.com/MaterialDesignInXAML/MaterialDesignInXamlToolkit/pull/3624

I would set the default namespace for the shared project. So that the analyzer doesn't flag the files as not matching the project name.

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[JLdgu]

@Keboo On Discord I asked whether the namespace of the shared project should be MaterialDesignDemo.Shared in order to explicitly highlight shared code. @michaelmairegger said it should. If you want me to change the namespace should I included it in this PR or have this one merged and raise a new PR?

[Keboo]

@Keboo On Discord I asked whether the namespace of the shared project should be MaterialDesignDemo.Shared in order to explicitly highlight shared code. @michaelmairegger said it should. If you want me to change the namespace should I included it in this PR or have this one merged and raise a new PR?

ah sorry, I have been in the process of moving and have kept up. I am fine with it being a separate PR so we can get this one in.