[docs] Missing information about the dotnet container steps around image being built locally

[HugoDurana]

Issue:

• The dotnet container step performs a local build of the image that is to be used by the aspire CLI - in this case aspire deploy. However the fact that this local step happens is not reflected on our documentation.
• This can lead to people having Docker Containers on Windows locally, and therefore any Linux image is likely to fail to build locally.

ASK:

• Clarify in our CLI documentation that the local containers must be exactly the same OS as the image that is defined in the AppHost.