add Coder as adopter

Created by: bpmct

code-server 4.0.0 uses open-vsx as the default registry: https://github.com/coder/code-server/releases/tag/v4.0.0

cc @jsjoeio

Created by: bpmct

I signed the ECA, but am running into issues matching my email. I emailed the webmaster at eclipse dot org for help.

Created by: bpmct

fixed the ECA issue

approved this merge request