- This ensures that other values than just the arrays are overridden, like nested objects, where it makes sense
- merge_depth is set to 3 so that top-level language features are merged (like 'scope'), but everything deeper is overridden with the user-config
We merge the elements of arrays for the top-level array. For
`languages.toml`, this is the array of languages. For any nested
arrays, we simply take the `right` array as-is instead of using
the union of `left` and `right`.
closes#1000