Add a note to creating a new compilation object after adding a source in source generators overview

[Youssef1313]

See https://stackoverflow.com/questions/69853257/sourcegenerator-attribute-constructorarguments-is-empty.

From the OP on Discord:

This scenario is really very very common that I think should be noted, since this is the number 1 article in Google search results, where people will expect to find this kind of information.

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Document Details

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• ID: 99a4410c-4c8d-0107-845b-9a951bb76682
• Version Independent ID: f1ed9873-3e29-b4bd-2dbb-44dd9a05d790
• Content: Source Generators
• Content Source: docs/csharp/roslyn-sdk/source-generators-overview.md
• Product: dotnet-csharp
• Technology: csharp-roslyn
• GitHub Login: @BillWagner
• Microsoft Alias: wiwagn

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Associated WorkItem - 331102

[BillWagner]

Adding @mikadumont

[BillWagner]

I was going through the issues on this article. I'd like to address this by making a new tutorial with more of a real world scenario using attributes.