Fix OclifUX.ux.prompt() return type

It's been a long standing issue that prompt returns a Promise<any> when
it clearly should return Promise<string>. It's because the wrapper
methods pauseAsync() don't forward their types along from the wrapped
functions.

src/cli-ux/action/base.ts

@@ -92,7 +92,7 @@ export class ActionBase {
     task.status = status
   }
 
-  public async pauseAsync(fn: () => Promise<any>, icon?: string) {
+  public async pauseAsync<T extends any>(fn: () => Promise<T>, icon?: string): Promise<T> {
     const task = this.task
     const active = task && task.active
     if (task && active) {

src/cli-ux/prompt.ts

@@ -120,9 +120,9 @@ function _prompt(name: string, inputOptions: Partial<IPromptOptions> = {}): Prom
  * prompt for input
  * @param name - prompt text
  * @param options - @see IPromptOptions
- * @returns void
+ * @returns Promise<string>
  */
-export function prompt(name: string, options: IPromptOptions = {}) {
+export function prompt(name: string, options: IPromptOptions = {}): Promise<string> {
   return config.action.pauseAsync(() => {
     return _prompt(name, options)
   }, chalk.cyan('?'))
@@ -149,9 +149,9 @@ export function confirm(message: string): Promise<boolean> {
 /**
  * "press anykey to continue"
  * @param message - optional message to display to user
- * @returns Promise<void>
+ * @returns Promise<string>
  */
-export async function anykey(message?: string): Promise<void> {
+export async function anykey(message?: string): Promise<string> {
   const tty = Boolean(process.stdin.setRawMode)
   if (!message) {
     message = tty ?