Add acs-plat-web to represent availability only in Web platform

Author: elavarasidc

articles/zone-pivot-groups.yml

@@ -1262,6 +1262,12 @@ groups:
     title: Android
   - id: platform-ios
     title: iOS
+- id: acs-plat-web
+  title: Platform
+  prompt: Choose a platform
+  pivots:
+  - id: platform-web
+    title: Web
 - id: acs-plat-azp-js
   title: Platform
   prompt: Choose a platform