Added no/multi from header condition

FAQ.md

@@ -2407,7 +2407,7 @@ $$flagged$
 $$deleted$
 ```
 
-To match *passed* message checks via a header condition (since version 1.1787):
+To match *passed* message checks via a header condition (since version 1.1787; no/multi-from since version 1.1791):
 
 ```
 $$dkim$
@@ -2416,6 +2416,8 @@ $$dmarc$
 $$mx$
 $$blocklist$
 $$replydomain$
+$$nofrom$
+$$multifrom$
 ```
 
 Note that *regex* should be disable and that there should be no white space.

app/src/main/java/eu/faircode/email/EntityRule.java

@@ -283,6 +283,12 @@ public class EntityRule {
                     } else if ("$replydomain".equals(keyword)) {
                         if (!Boolean.TRUE.equals(message.reply_domain))
                             return false;
+                    } else if ("$nofrom".equals(keyword)) {
+                        if (message.from != null && message.from.length > 0)
+                            return false;
+                    } else if ("$multifrom".equals(keyword)) {
+                        if (message.from == null || message.from.length < 2)
+                            return false;
                     } else {
                         List<String> keywords = new ArrayList<>();
                         keywords.addAll(Arrays.asList(message.keywords));