Also support string in shellArgs passed directly to createTerminal

Part of #70716

src/vs/vscode.d.ts

@@ -6599,10 +6599,11 @@ declare module 'vscode' {
 		 *
 		 * @param name Optional human-readable string which will be used to represent the terminal in the UI.
 		 * @param shellPath Optional path to a custom shell executable to be used in the terminal.
-		 * @param shellArgs Optional args for the custom shell executable.
+		 * @param shellArgs Optional args for the custom shell executable. A string can be used on Windows only which
+		 * allows specifying shell args in [command-line format](https://msdn.microsoft.com/en-au/08dfcab2-eb6e-49a4-80eb-87d4076c98c6).
 		 * @return A new Terminal.
 		 */
-		export function createTerminal(name?: string, shellPath?: string, shellArgs?: string[]): Terminal;
+		export function createTerminal(name?: string, shellPath?: string, shellArgs?: string[] | string): Terminal;
 
 		/**
 		 * Creates a [Terminal](#Terminal). The cwd of the terminal will be the workspace directory

src/vs/workbench/api/node/extHost.api.impl.ts

@@ -474,7 +474,7 @@ export function createApiFactory(
 			createWebviewPanel(viewType: string, title: string, showOptions: vscode.ViewColumn | { viewColumn: vscode.ViewColumn, preserveFocus?: boolean }, options: vscode.WebviewPanelOptions & vscode.WebviewOptions): vscode.WebviewPanel {
 				return extHostWebviews.createWebviewPanel(extension, viewType, title, showOptions, options);
 			},
-			createTerminal(nameOrOptions?: vscode.TerminalOptions | string, shellPath?: string, shellArgs?: string[]): vscode.Terminal {
+			createTerminal(nameOrOptions?: vscode.TerminalOptions | string, shellPath?: string, shellArgs?: string[] | string): vscode.Terminal {
 				if (typeof nameOrOptions === 'object') {
 					return extHostTerminalService.createTerminalFromOptions(<vscode.TerminalOptions>nameOrOptions);
 				}

src/vs/workbench/api/node/extHostTerminalService.ts

@@ -293,7 +293,7 @@ export class ExtHostTerminalService implements ExtHostTerminalServiceShape {
 		this._proxy = mainContext.getProxy(MainContext.MainThreadTerminalService);
 	}
 
-	public createTerminal(name?: string, shellPath?: string, shellArgs?: string[]): vscode.Terminal {
+	public createTerminal(name?: string, shellPath?: string, shellArgs?: string[] | string): vscode.Terminal {
 		const terminal = new ExtHostTerminal(this._proxy, name);
 		terminal.create(shellPath, shellArgs);
 		this._terminals.push(terminal);