Create type definition for 'recaptcha-promise' (#4068)

src/@types/recaptcha-promise.d.ts

@@ -0,0 +1,16 @@
+declare module 'recaptcha-promise' {
+	interface IVerifyOptions {
+		secret_key?: string;
+	}
+
+	interface IVerify {
+		(response: string, remoteAddress?: string): Promise<boolean>;
+		init(options: IVerifyOptions): IVerify;
+	}
+
+	namespace recaptchaPromise {} // Hack
+
+	const verify: IVerify;
+
+	export = verify;
+}