[prompts] Fix type and validate function definitions (#35510)

* Allow `type` function to return `Falsy`

As defined in the documentation here: https://github.com/terkelg/prompts#type

The `type` field can be a function which returns a `Falsy` value to disable the prompt, which is currently not allowed by these type definitions:

> If `type` is a falsy value the prompter will skip that question.

* fix validate return type

types/prompts/index.d.ts

@@ -1,4 +1,4 @@
-// Type definitions for prompts 2.04
+// Type definitions for prompts 2.0
 // Project: https://github.com/terkelg/prompts
 // Definitions by: Berkay GURSOY <https://github.com/Berkays>
 //                 Daniel Perez Alvarez <https://github.com/danielpa9708>
@@ -60,13 +60,13 @@ declare namespace prompts {
     }
 
     interface PromptObject<T extends string = string> {
-        type: ValueOrFunc<PromptType> | Falsy;
+        type: PromptType | Falsy | PrevCaller<T, PromptType | Falsy>;
         name: ValueOrFunc<T>;
         message?: ValueOrFunc<string>;
         initial?: string | number | boolean | Date;
         style?: string;
         format?: PrevCaller<T, void>;
-        validate?: PrevCaller<T, void>;
+        validate?: PrevCaller<T, boolean | string>;
         onState?: PrevCaller<T, void>;
         min?: number;
         max?: number;

types/prompts/prompts-tests.ts

@@ -12,3 +12,23 @@ type HasProperty<T, K> = K extends keyof T ? true : false;
     const HasPropValue: HasProperty<typeof response, "value"> = true;
     const DoesntHavePropAsdf: HasProperty<typeof response, "asdf"> = false;
 })();
+
+(async () => {
+    await prompts([
+        {
+            type: 'text',
+            name: 'language',
+            message: "What langauge is the next greatest thing since sliced bread?",
+        },
+        {
+            type: (prev, values) => {
+                const HasPromptName: HasProperty<typeof values, "language"> = true;
+                const DoesntHavePromptTypes: HasProperty<typeof values, "text"> = false;
+
+                return prev === 'javascript' ? 'confirm' : null;
+            },
+            name: 'confirmation',
+            message: "Have you tried TypeScript?"
+        }
+    ]);
+})();