Add doc for executeTask and openTunnel

src/vs/vscode.d.ts

@@ -6285,6 +6285,10 @@ declare module 'vscode' {
 		 * Executes a task that is managed by VS Code. The returned
 		 * task execution can be used to terminate the task.
 		 *
+		 * @throws When running a ShellExecution or a ProcessExecution
+		 * task in an environment where a new process can't be started.
+		 * In such an environment, only CustomExecution tasks can be run.
+		 *
 		 * @param task the task to execute
 		 */
 		export function executeTask(task: Task): Thenable<TaskExecution>;

src/vs/vscode.proposed.d.ts

@@ -344,6 +344,9 @@ declare module 'vscode' {
 		/**
 		 * Forwards a port. If the current resolver implements RemoteAuthorityResolver:forwardPort then that will be used to make the tunnel.
 		 * By default, openTunnel only support localhost; however, RemoteAuthorityResolver:tunnelFactory can be used to support other ips.
+		 *
+		 * @throws When run in an environment without a remote.
+		 *
 		 * @param tunnelOptions The `localPort` is a suggestion only. If that port is not available another will be chosen.
 		 */
 		export function openTunnel(tunnelOptions: TunnelOptions): Thenable<Tunnel>;