State of the ANGLE support

[mak8kammerer]

Hi! While reading the wgpu wiki and source code, I was a bit confused about ANGLE support.

The Running on ANGLE topic from the wiki suggests that ANGLE is supported on all major desktop platforms (Windows, Linux, macOS), whereras wgpu's Cargo.toml stated only macOS support:

wgpu/wgpu/Cargo.toml

Lines 74 to 75 in f14458b

	## Enables the GLES backend on macOS only for use with [ANGLE](https://github.com/google/angle).
	angle = ["wgpu-core?/angle"]

So, the questions are:

1. Is ANGLE support in wgpu limited only to macOS?
2. If not, how can I enable ANGLE support in (Windows/Linux) wgpu app (for example, in wgpu-info)?

Тhank in advance.