* Fix DPI with 0 width/hight reported by xorg
* Add `WINIT_HIDPI_FACTOR` env variable
It is now possible to override the DPI factor using the
`WINIT_HIDPI_FACTOR` environment variable on X11.
The changelog also has been updated to introduce all current changes
made.
* Add documentation for the environment variable
* Fix nitpicks
* Learning the alphabet
* Panic with error message if DPI env var is <= 0
