Add email notification option ATTENTION_SET_ONLY

This new option was recently added to the backend in change 284133.

Change-Id: Ifef2aed071f646d4694fad48f8e7d47846ded8c3
diff --git a/polygerrit-ui/app/constants/constants.ts b/polygerrit-ui/app/constants/constants.ts
index 2db076f..be52835 100644
--- a/polygerrit-ui/app/constants/constants.ts
+++ b/polygerrit-ui/app/constants/constants.ts
@@ -292,6 +292,7 @@
 export enum EmailStrategy {
   ENABLED = 'ENABLED',
   CC_ON_OWN_COMMENTS = 'CC_ON_OWN_COMMENTS',
+  ATTENTION_SET_ONLY = 'ATTENTION_SET_ONLY',
   DISABLED = 'DISABLED',
 }
 
diff --git a/polygerrit-ui/app/elements/settings/gr-settings-view/gr-settings-view_html.ts b/polygerrit-ui/app/elements/settings/gr-settings-view/gr-settings-view_html.ts
index ea26a51..78f84b1 100644
--- a/polygerrit-ui/app/elements/settings/gr-settings-view/gr-settings-view_html.ts
+++ b/polygerrit-ui/app/elements/settings/gr-settings-view/gr-settings-view_html.ts
@@ -175,6 +175,9 @@
               <select>
                 <option value="CC_ON_OWN_COMMENTS">Every comment</option>
                 <option value="ENABLED">Only comments left by others</option>
+                <option value="ATTENTION_SET_ONLY"
+                  >Only when I am in the attention set</option
+                >
                 <option value="DISABLED">None</option>
               </select>
             </gr-select>