Add amdgpu target to ecosystem page

[LegNeato]

Looks like this target was recently revived:

rust-lang/rust#134740

@Flakebi is it ok if I add it to https://rust-gpu.github.io/ecosystem/ or is it too early? Also, I'd love to chat with you about some rust & GPU related stuff but I can't find an email or twitter and I can't message you on github. Can you DM me or email me? My email is my first name at my last name dot com.