Expose adding files and folders in sql database projects (#14391)

* expose addToProject in dataworkspace.d.ts

* remove changes in data workspace extension

* add sqldbproj.d.ts

* change list to be Uris instead of strings

* don't add files/folders if any don't exist

* fix test on windows

extensions/data-workspace/src/common/dataWorkspaceExtension.ts

@@ -31,5 +31,4 @@ export class DataWorkspaceExtension implements IExtension {
 	validateWorkspace(): Promise<boolean> {
 		return this.workspaceService.validateWorkspace();
 	}
-
 }