Invalid editorconfig

[vbgl]

Whenever neovim is launched (version 0.9.5), the following warning is displayed. This is quite annoying.

editorconfig: invalid value for option charset: utf8. charset must be one of "utf-8", "utf-8-bom", "latin1", "utf-16b
e", or "utf-16le"

cc Gaëtan (@cassiersg)