I'm sure someone already has created vim syntax highlighting for ion, but I couldn't find anything with a quick search, so I created my own. You can find it at github. Will probably be updated as I get to write more ion code.
So many people do a .tmLanguage but i did already make one it works for
sublime/vscode/textmate/vs so if you want you can download it.
Don't hesitate to make a pull request or opening an issue.
Will probably add Atom also in Future and if i get the vs extension done it
will also be better integrated with Visual Studio.