Add warning for untrusted .NET templates (#49074)

* Add warning for untrusted .NET templates

Added a warning about untrusted .NET templates.

* Respond to PR feedback

* Apply suggestions from code review

Co-authored-by: Meaghan Osagie (Lewis) <mosagie@microsoft.com>

* Move warning for untrusted .NET templates to description

Reinstate warning about untrusted .NET templates.

---------

Co-authored-by: Meaghan Osagie (Lewis) <mosagie@microsoft.com>

Author: marcpopMSFT

docs/core/tools/custom-templates.md

@@ -230,6 +230,9 @@ project_folder
 
 Use the [dotnet new install](dotnet-new-install.md) command to install a template package.
 
+> [!WARNING]
+> Templates can run MSBuild code when triggered, don't install or run untrusted .NET templates.
+
 ### To install a template package from a NuGet package stored at nuget.org
 
 Use the NuGet package identifier to install a template package.

docs/core/tools/dotnet-new-install.md

@@ -42,6 +42,9 @@ Starting with .NET SDK 6.0.100, installed template packages are available in lat
 >   dotnet new --install Microsoft.Azure.WebJobs.ProjectTemplates
 >   ```
 
+> [!WARNING]
+> Templates can run MSBuild code when triggered, don't install or run untrusted .NET templates.
+
 ## Arguments
 
 - **`<PATH|NUGET_ID>`**