Trigger generators when saving input files

## Is your feature request related to a problem? Please describe.
As part of my .csproj, I have a C# source file generated from an XML/XSLT pair of files (see snippet below).

In Visual Studio, this source will regenerate when saving edits to the XML or XSLT files. But vscode does not trigger when saving.

## Describe the solution you would like
I would like edits to the generator input files to trigger a regen of the output source file.

## Additional context
Here is how I have source-file generation set up:

```

MSBuild:_SettingsCs


MSBuild:_SettingsCs











$(CoreCompileDependsOn);SettingsCs

```