Does not detect vale configuration when using multi-root workspace

[dkwon17]

My project has a .vscode/settings.json file with the following content:

{
    "vale.valeCLI.config": "<absolute path to project>/.custom.ini",
}

When this project is imported in a multi-root workspace in VS Code, my custom value config file .custom.ini is not being used.

To reproduce the problem:

1. Clone this project: https://github.com/dkwon17/vale-boilerplate/tree/testing
2. In the .vscode/settings.json file, edit the value of vale.valeCLI.config value so that it is the correct absolute path for your machine
3. Open VS Code with vale-vscode installed
4. Open the project as a multi-root workspace by clicking on add a folder instead of Open Folder:
   
5. Open the command palette and run Developer: Reload Window
6. Open the README.md file and notice that there are no vale warnings:
   

Expected behaviour:
I expected that the behaviour would be the same as when opening the project folder via clicking Open Folder. In this case, the vale configuration is being read and warnings appear: