"GIGA Display Shield 3D Engine Tutorial" requires LVGL v8.x

[MaffooClock]

When following the GIGA Display Shield 3D Engine Tutorial the user is likely to encounter this error in the console when they attempt to compile and upload:

Gears.ino: In function 'void setup()':
Gears.ino:112:56: error: 'LV_IMG_CF_TRUE_COLOR' was not declared in this scope
   lv_canvas_set_buffer(canvas, cbuf, WINDOWX, WINDOWY, LV_IMG_CF_TRUE_COLOR);
                                                        ^~~~~~~~~~~~~~~~~~~~

This is because the default version of the LVGL library to be installed is v9.x, but the Gears demo (in v0.0.1 of the Arduino_GigaDisplay_TinyGL library, renamed from Arduino_TinyGL) depends on LVGL v8.x.

The maintainer of the Arduino_GigaDisplay_TinyGL library has addressed this in commit 77983a0, but has not published a new release.

Until a new release has been published, tutorial followers will need to be advised to:

1. specify v8.4 of the LVGL library
2. or manually install the Arduino_GigaDisplay_TinyGL library
3. or manually add the change from that commit to their Gears.ino