This class ``` javascript class ClassName { async methodName(arg1) { } } ``` should have `async` keyword highlighted as `jsAsyncKeyword`. But it is not. It just have `jsClassBlock`. If I'm correct adding `jsAsyncKeyword` to [this line](https://github.com/pangloss/vim-javascript/blob/master/syntax/javascript.vim#L138) should fix this, because it works for me.