Keyboard improvements (#240)

- Renamed various keyboard functions so it's easier to differentiate hardware versus software keyboard functionality
- Created `Tactility/lvgl/Keyboard.h` as a proxy  for the internal `Gui` service.
- Implemented `tt_lvgl_keyboard.h` in `TactilityC`.

Tactility/Source/lvgl/Keyboard.cpp

@@ -0,0 +1,44 @@
+#include "Tactility/lvgl/Keyboard.h"
+#include "Tactility/service/gui/Gui.h"
+
+namespace tt::lvgl {
+
+static lv_indev_t* keyboard_device = nullptr;
+
+void software_keyboard_show(lv_obj_t* textarea) {
+    service::gui::softwareKeyboardShow(textarea);
+}
+
+void software_keyboard_hide() {
+    service::gui::softwareKeyboardHide();
+}
+
+bool software_keyboard_is_enabled() {
+    return service::gui::softwareKeyboardIsEnabled();
+}
+
+void software_keyboard_activate(lv_group_t* group) {
+    if (keyboard_device != nullptr) {
+        lv_indev_set_group(keyboard_device, group);
+    }
+}
+
+void software_keyboard_deactivate() {
+    if (keyboard_device != nullptr) {
+        lv_indev_set_group(keyboard_device, nullptr);
+    }
+}
+
+bool hardware_keyboard_is_available() {
+    return keyboard_device != nullptr;
+}
+
+void hardware_keyboard_set_indev(lv_indev_t* device) {
+    keyboard_device = device;
+}
+
+void keyboard_add_textarea(lv_obj_t* textarea) {
+    service::gui::keyboardAddTextArea(textarea);
+}
+
+}