When manually creating the project and adding shader files FXC acts up

Looks like when you add hlsl files manually to a project via Add New File it creates `` elements in the project file, which can cause a problem, as in vs tries to compile the files itself using `fxc.exe`.

```
1>an error occurred while setting the initial search directory.
1>searches will be relative to the application's starting directory.
1>compilation failed; no code produced
```

We should adjust the wording in the early chapters somewhere, that this can happen and a workaround is to manually remove `` elements from the project file.

Review the early tutorial chapters for the project-creation steps involving manually added HLSL files. Confirm where Visual Studio can add elements and document the reported FXC failure plus the stated workaround of removing those elements from the project file. Done means the warning and workaround appear in the relevant early chapter.

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