Show suggestions for known matchVariant values

[thecrypticace]

Given this variant:

matchVariant(
  "foo",
  (value) => `&:is([data-foo='${value}'])`,
  {
    values: {
      DEFAULT: "",
      bar: "bar",
      baz: "bar",
    },
  }
)

We weren't listing foo-bar and foo-baz in IntelliSense. This PR fixes that.