Add initialText proposed API

Part of #120368

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

@@ -633,6 +633,9 @@ export function createApiFactoryAndRegisterActors(accessor: ServicesAccessor): I
 					if ('pty' in nameOrOptions) {
 						return extHostTerminalService.createExtensionTerminal(nameOrOptions);
 					}
+					if (nameOrOptions.initialText) {
+						checkProposedApiEnabled(extension);
+					}
 					return extHostTerminalService.createTerminalFromOptions(nameOrOptions);
 				}
 				return extHostTerminalService.createTerminal(nameOrOptions, shellPath, shellArgs);