Revert back index.bs before the speculative deletion

Author: yoshisatoyanagisawa

docs/index.bs

@@ -4,8 +4,11 @@ Status: ED
 ED: https://w3c.github.io/ServiceWorker/
 TR: https://www.w3.org/TR/service-workers/
 Shortname: service-workers
+Level:
 Editor: Jake Archibald, w3cid 76394, Google, [email protected]
 Editor: Marijn Kruisselbrink, w3cid 72440, Google, [email protected]
+Former Editor: Alex Russell, Google, [email protected]
+Former Editor: Jungkee Song, Microsoft‚ represented Samsung until April 2018, [email protected]
 Repository: w3c/ServiceWorker
 Group: serviceworkers
 !Tests: <a href=https://github.com/web-platform-tests/wpt/tree/master/service-workers>web-platform-tests service-workers/</a> (<a href=https://github.com/web-platform-tests/wpt/labels/service-workers>ongoing work</a>)