Implement support for localizing file content.
Example use case for this requirement is localizing comments in code files (this cannot be done via resource files).

Example of using comments/strings in templates:

• famous Hello, World! in console template: https://github.com/dotnet/sdk/blob/11f4fee47293e8c9dae5fa902074eb26062d8f99/template_feed/Microsoft.DotNet.Common.ProjectTemplates.8.0/content/ConsoleApplication-CSharp/Program.cs#L18
• comment in console template: https://github.com/dotnet/sdk/blob/11f4fee47293e8c9dae5fa902074eb26062d8f99/template_feed/Microsoft.DotNet.Common.ProjectTemplates.8.0/content/ConsoleApplication-CSharp/Program.cs#L2

Kick off for this work is: #3432