Added FAQ

FAQ.md

@@ -119,6 +119,14 @@ Progressive search is a pro feature.
 To use Outlook with two factor authentication enabled, you need to create an app password.
 See [here](https://support.microsoft.com/en-us/help/12409/microsoft-account-app-passwords-two-step-verification) for the details.
 
+<a name="FAQ15"></a>
+**(15) Can you add ... ?**
+
+* Account colors: the goal is to keep the app as simple as possible, so this will not be added.
+* LED notifications: there are less and less devices with a notification light and if there is one, it can mostly be managed by Android, so there is little point in adding support for this.
+* Encryption: there is too little interest in sending/receiving encrypted messages to justifiy putting effort into this.
+* POP/poll support: besides that any decent provider is supporting / should support IMAP, polling does consume extra battery power and will delay notification of new messages, so this will not be added.
+
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 If you have another question, you can use [this forum](https://forum.xda-developers.com/android/apps-games/source-email-t3824168).