Explicitly specify supported modes of all meters

This reduces code size by not needing to check if 'supportedModes' is
zero.
diff --git a/TasksMeter.c b/TasksMeter.c
index aa41e63..fc1e4b0 100644
--- a/TasksMeter.c
+++ b/TasksMeter.c
@@ -72,6 +72,7 @@
    },
    .updateValues = TasksMeter_updateValues,
    .defaultMode = TEXT_METERMODE,
+   .supportedModes = METERMODE_DEFAULT_SUPPORTED,
    .maxItems = 4,
    .total = 100.0,
    .attributes = TasksMeter_attributes,