Preserve legal comments from third party dependencies

When bundling, esbuild discards all comments from the code. This could give the impression that the third-party dependencies that come bundled in axe-core fall under Deque's copyright statement at the top of axe.js.

This is solved by ESBuils 13+, which by default preserves legal comments. But because axe-core is pinned on ESBuild 11 we're missing out on this important feature.