feat: change axis line colors

src/css/charts.scss

@@ -1,6 +1,6 @@
 :root {
 	--fr-label-color: #313b44;
-	--fr-axis-line-color:  #E2E6E9;
+	--fr-axis-line-color:  #F4F5F6;
 
 	--fr-stroke-width: 2px;
 	--fr-dataset-circle-stroke: #FFFFFF;