event-widget: draw horizontal timed events differently

This makes more clear which events are timed, and which events
are all day. They are also super cute!

src/css-code.h

@@ -23,6 +23,14 @@
 ".color-%1$d {"\
 "  background-color: %2$s"\
 "}"\
+".color-%1$d.horizontal.timed:dir(ltr) {"\
+"  background-color: transparent;"\
+"  border-left: solid 4px %2$s;"\
+"}"\
+".color-%1$d.horizontal.timed:dir(rtl) {"\
+"  background-color: transparent;"\
+"  border-right: solid 4px %2$s;"\
+"}"\
 ".color-%1$d.slanted {"\
 "  background-color: transparent;"\
 "  background-image: linear-gradient(100deg, /* left edge */"\