* Added 'KIVY_SDL_GL_ALPHA_SIZE' environmental variable, so X11 is not required when using SDL2 in a headless environment
Thanks to @ddimensia for figuring it out
* Updated the installation instructions for Raspberry Pi 4 headless installation on Raspbian Buster, as it no longer requires X11 to be installed
* Automatically set the SDL_GL_ALPHA_SIZE to 0 when running on a Raspberry Pi
* Set 'KIVY_SDL_GL_ALPHA_SIZE=0' when building using the CI, so cross compiling of the wheels works
* Make sure KIVY_SDL_GL_ALPHA_SIZE is an int
* Cross compile wheel for armv7l (Raspberry Pi 4) using Github Actions CI
Fixes#6567
* Added instruction on how to install Kivy on a Raspberry Pi 4
* Do not package the examples in the wheel
* We can not upload armv7l wheels to PyPI
* Remove all references to KivyPie
* Merge the installations instructions for Raspberry Pi's together
* Build the armv7l wheel on Stretch as well
* Create a copy of the wheel with a armv6l suffix
* The wheels are Raspberry Pi specific