Highlight trailing whitespace(s) of the inserted lines

syntax/diff.syntax

@@ -15,7 +15,9 @@ context linestart \+\+\+ \n brightmagenta
 context linestart \*\*\* \n brightmagenta
 context linestart === \n brown
 context linestart \+ \n brightgreen
+    keyword \{\s\t\}\[\s\t\]\n white red
 context linestart > \n brightgreen
+    keyword \{\s\t\}\[\s\t\]\n white red
 context linestart - \n brightred
 context linestart < \n brightred
 context linestart ! \n yellow