Syntax highlighting incorrect with "bs" attributes on records

Example from the bucklescript docs, where `deriving abstract` is used to map a record type to an object:
https://bucklescript.github.io/docs/en/object#optional-labels

```
[@bs.deriving abstract]
type person = {
[@bs.optional] name: string,
age: int,
job: string,
};
```

Screenshot of the same (I'm using flatland monokai theme):

Note how `bs` picks up the field name highlighting which breaks all highlighting before the `:`

There are many possible attributes, all break the same way. I'm using `[@bs.as]` to rename a field.

Reproduce the BuckleScript record example from the linked documentation, including [@bs.deriving abstract] and [@bs.optional], in the language server's editor integration. Inspect how Reason attributes are tokenized and verify that the bs attribute does not consume the following field name or disrupt highlighting before the colon. Done means the shown attributes and the surrounding record fields receive correct syntax highlighting.

Written by the indexing model from the issue text.