Add support to Adafruit_LvGL_Glue

[viniciusmiguel]

This library does not inherit Adafruit_SPITFT so it cannot be used with LvGL Glue.
Please update the library for compatibility with Adafruit_LvGL_Glue.

[ladyada]

hi we have no plans to do so, if someone submits a PR we'd check it out. the two graphics systems are not very similar - it may not be an easy merge!

[makermelissa]

I've gotten Little VGL running on an RA8875 a couple of years ago (before Adafruit_LvGL_Glue existed) and even with some drawing optimizations I implemented, it was a relatively slow drawing experience because the RA8875 is designed to make special use of hardware accelerated drawing functions rather than pixel by pixel drawing. I ended up going with the smaller ILI9341 displays and it was a much better experience.