Added docs for X::DateTime::TimezoneClash

Author: Jan-Olof Hendig

doc/Type/X/DateTime/TimezoneClash.pod

@@ -0,0 +1,22 @@
+=begin pod
+
+=TITLE class X::DateTime::TimezoneClash
+
+=SUBTITLE Error due to using both timezone offset and :timezone
+
+    class X::DateTime::TimezoneClash does X::Temporal is Exception { }
+
+This exception is thrown when code tries to create a C<DateTime> object
+specifying both a timezone offset and the named argument C<:timezone>.
+
+    say DateTime.new('2015-12-24T12:23:00+0200');                   # works
+    say DateTime.new('2015-12-24T12:23:00', timezone => 7200);      # works
+    say DateTime.new('2015-12-24T12:23:00+0200', timezone => 7200); # exception
+
+=head1 Methods
+
+=head2 message
+
+Returns 'DateTime.new(Str): :timezone argument not allowed with a timestamp offset'
+
+=end pod