[Feature] Missing LVGL 9.5 Widget Headers and ArcLabel Refinements

[pedapudi]

Description

Several new LVGL 9.5 widgets are missing from the main lvgl_cpp.h header:

• ArcLabel
• 3DTexture
• GLTF

Also, ArcLabel lacks a consolidated set_angles(start, size) method and get_text() is currently returning a hardcoded empty string.

Proposed Fix

1. Update lvgl_cpp.h to include headers for the above widgets.
2. Add set_angles(lv_value_precise_t start, lv_value_precise_t size) to ArcLabel.
3. Update ArcLabel::get_text() to return nullptr or implement the getter if available in the C API.

[pedapudi]

Updated 'lvgl_cpp.h' to include headers for ArcLabel, 3DTexture, GLTF, and Screen. Added 'set_angles(start, size)' to ArcLabel and updated 'get_text()' to return nullptr since no getter exists in the C API.