[Feature] Improve responsiveness of ancillary-menu

## Problem
Now, the language selection is overflowing in the ancillary menu of cc-legal-tools-app. (See: [cc-legal-tools-app#418](https://github.com/creativecommons/cc-legal-tools-app/issues/418)).

## Description
We need to set the font size in more detail to fix this. I wrote CSS like this and the problem was fixed in [my PR](https://github.com/creativecommons/cc-legal-tools-app/pull/488):
```
.ancilliary-menu {
font-size: min(.8em, 2.5vw);
}
```

## Additional context
I created a [PR](https://github.com/creativecommons/cc-legal-tools-app/pull/488) for the cc-legal-tools-app and overrode the font size of `.ancilliary-menu`. This needs to be fixed [cc-legal-tools-app#418](https://github.com/creativecommons/cc-legal-tools-app/issues/418) without using Media queries/breakpoints.

## Alternatives
Media queries/breakpoints can be used to specify font size, but I think this method is better.

## Implementation

- [x] I would be interested in implementing this feature.