yargs: Add scriptName method according to http://yargs.js.org/docs/#api-scriptname0 (#27234)

types/yargs/index.d.ts

@@ -185,6 +185,8 @@ declare namespace yargs {
          */
         reset(): Argv;
 
+        scriptName($0: string): Argv;
+
         showCompletionScript(): Argv;
 
         showhidden(option?: string | boolean): Argv;

types/yargs/yargs-tests.ts

@@ -661,3 +661,8 @@ function Argv$showhidden() {
         .showhidden('show-hidden')
         .showhidden('show-hidden', 'Show hidden options');
 }
+
+function Argv$scriptName() {
+    const ya = yargs
+        .scriptName("my-script");
+}