Unknown property: 'appearance' in Diagnostics view

[richiksc]

The property 'appearance' is not recognized by the CSS language server in the Diagnostics view. There is an alert next to the line where the property appearance is declared and a message shows up in Diagnostics:

However, the vendor prefixed versions are recognized and no error is thrown. Most developers like to include the unprefixed version as well, despite it being not used by any browsers, for future proofing and adherence to CSS standards and specifications.