Added missing sum keyword

gilmaimon · gilmaimon · commit 6bc7ae75abda · 2019-01-06T00:26:31.000+02:00
diff --git a/keywords.txt b/keywords.txt
@@ -24,4 +24,5 @@ datetime	KEYWORD2
 max	KEYWORD2
 min	KEYWORD2
 avg	KEYWORD2
-count	KEYWORD2
+count	KEYWORD2
+sum	KEYWORD2
