Adding note to “service-workers mode”

Author: jakearchibald

fetch.bs

@@ -709,6 +709,24 @@ this flag set are subject to additional processing requirements.
 "<code>foreign</code>", or "<code>none</code>". Unless stated otherwise it is
 "<code>all</code>".
 
+<div class=note>
+ This determines which service workers will receive a {{fetch!!event}} event for this fetch.
+
+ <dl>
+  <dt>"<code>all</code>"
+  <dd>Relevant local and foreign service workers will get a {{fetch!!event}} or
+   {{foreignfetch!!event}} event for this fetch.
+
+  <dt>"<code>foreign</code>"
+  <dd>Only relevant foreign service workers will get a {{foreignfetch!!event}} event for this fetch.
+  {{fetch(input)!!method}} uses this to bypass the current service worker if the global is a
+  {{ServiceWorkerGlobalScope}}.
+
+  <dt>"<code>none</code>"
+  <dd>Neither local nor foreign service workers will get events for this fetch.
+ </dd>
+</div>
+
 <p>A <a for=/>request</a> has an associated
 <dfn export for=request id=concept-request-initiator>initiator</dfn>, which is
 the empty string,