Add for_window --always

This allows a for_window command to trigger multiple times on the same window;
the default is to only run the command once (when it first matches).

This can be useful to apply rules to applications like VLC that hide and show a
window without re-creating it (when using the taskbar icon to hide/show).

include/sway/criteria.h

@@ -45,6 +45,7 @@ struct criteria {
 #endif
 	bool floating;
 	bool tiling;
+	bool always;
 	char urgent; // 'l' for latest or 'o' for oldest
 	struct pattern *workspace;
 	pid_t pid;