CSSOrigin typedef
CSSOrigin = String
https://developer.chrome.com/docs/extensions/reference/extensionTypes/#type-RunAt
document_start
,document_end
,document_idle
https://developer.chrome.com/docs/extensions/reference/extensionTypes/#type-CSSOrigin
author
,user
Implementation
/// https://developer.chrome.com/docs/extensions/reference/extensionTypes/#type-CSSOrigin
/// `author`,`user`
typedef CSSOrigin = String;