Project restructuring (fixes macOS builds) (#198)

- Create `Include/` folder for all main projects
- Fix some issues here and there (found while moving things)
- All includes are now in `Tactility/` subfolder and must be included with that prefix. This fixes issues with clashing POSIX headers (e.g. `<semaphore.h>` versus Tactility's `Semaphore.h`)

TactilityHeadless/Include/Tactility/hal/Keyboard.h

@@ -0,0 +1,18 @@
+#pragma once
+
+#include "lvgl.h"
+
+namespace tt::hal {
+
+class Display;
+
+class Keyboard {
+public:
+    virtual bool start(lv_display_t* display) = 0;
+    virtual bool stop() = 0;
+    virtual bool isAttached() const = 0;
+
+    virtual lv_indev_t* _Nullable getLvglIndev() = 0;
+};
+
+}