swaybar: add status_edge_padding command

This adds the bar subcommand `status_edge_padding <padding>` to set the
padding used when the status line is on the right edge of the bar.

sway/config/bar.c

@@ -107,6 +107,7 @@ struct bar_config *default_bar_config(void) {
 	bar->pid = 0;
 	bar->modifier = get_modifier_mask_by_name("Mod4");
 	bar->status_padding = 1;
+	bar->status_edge_padding = 3;
 	if (!(bar->mode = strdup("dock"))) {
 	       goto cleanup;
 	}