Add FAQ entry for missing contacts

See #73 (comment)

app/src/main/res/values/strings.xml

@@ -84,10 +84,10 @@
     <!-- FAQ -->
     <string name="faq_1_title">I hear incoming calls, but the screen doesn\'t turn on. What can I do?</string>
     <string name="faq_1_text">Such issues can have many device and system specific reasons, hard to say in general. You should look around in your device settings and make sure that the app is allowed to pop up when in background and allow displaying over other apps.</string>
-
     <string name="faq_2_title">Why emergency calls don\'t work properly?</string>
     <string name="faq_2_text">Due to system restrictions, emergency calls can only be made through your system\'s default dialer or phone app. To ensure emergency calls work properly, you need to keep the system app installed and enabled.</string>
-
+    <string name="faq_3_title">Why are some of my contacts missing from the app?</string>
+    <string name="faq_3_text">Fossify Phone only displays contacts that have a phone number associated with them. Contacts without a phone number are not shown in the app.</string>
     <!--
         Haven't found some strings? There's more at
         https://github.com/FossifyOrg/Commons/tree/master/commons/src/main/res