Editorial: Add a space between following and perform the fetch hook (#1766)

This addresses #1765.

Author: yoshisatoyanagisawa

docs/index.bs

@@ -2379,7 +2379,7 @@ spec: storage; urlPrefix: https://storage.spec.whatwg.org/
     <section>
       <h4 id="importscripts">{{ServiceWorkerGlobalScope/importScripts(urls)}}</h4>
 
-      When the <dfn method for="ServiceWorkerGlobalScope" id="importscripts-method"><code>importScripts(|urls|)</code></dfn> method is called on a {{ServiceWorkerGlobalScope}} object, the user agent *must* <a>import scripts into worker global scope</a>, given this {{ServiceWorkerGlobalScope}} object and |urls|, and with the following[=fetching scripts/perform the fetch hook=] steps, given the [=/request=] |request|:
+      When the <dfn method for="ServiceWorkerGlobalScope" id="importscripts-method"><code>importScripts(|urls|)</code></dfn> method is called on a {{ServiceWorkerGlobalScope}} object, the user agent *must* <a>import scripts into worker global scope</a>, given this {{ServiceWorkerGlobalScope}} object and |urls|, and with the following [=fetching scripts/perform the fetch hook=] steps, given the [=/request=] |request|:
 
         1. Let |serviceWorker| be |request|'s [=request/client=]'s [=environment settings object/global object=]'s [=ServiceWorkerGlobalScope/service worker=].
         1. Let |map| be |serviceWorker|'s [=script resource map=].