JavaScript highlighting (fenced code blocks)

[mitchallen]

JavaScript keywords are not all being highlighted for blocks like this:

 ~~~{.javascript .numberLines caption="keywords.js"}

# Keywords

var a = "Alpha"
const b = "Beta"
let c = "Gamma"

~~~

In this case, only the const keyword is being highlighted. It seems like only generic keywords that could apply to many languages are being highlighted.

I'm building with the docker container using these parameters:

    --template eisvogel --listings

Do I need to pass in specific definitions for JavaScript?