Extract mouse processor trait

Mainly for consistency with the keyboard processor trait.

This could allow to provide alternative mouse processors.

app/src/mouse_inject.h

@@ -0,0 +1,24 @@
+#ifndef SC_MOUSE_INJECT_H
+#define SC_MOUSE_INJECT_H
+
+#include "common.h"
+
+#include <stdbool.h>
+
+#include "controller.h"
+#include "scrcpy.h"
+#include "screen.h"
+#include "trait/mouse_processor.h"
+
+struct sc_mouse_inject {
+    struct sc_mouse_processor mouse_processor; // mouse processor trait
+
+    struct controller *controller;
+    struct screen *screen;
+};
+
+void
+sc_mouse_inject_init(struct sc_mouse_inject *mi, struct controller *controller,
+                     struct screen *screen);
+
+#endif