feat: File input with preview

[dlnr]

Describe the pull request

PoC for File input that displays a file preview list. Based on the MDN example and using the FileList interface. This is a logical enrichment of the native file input that allows you to show file previews or a document icon.

What

This would need cleanup if this is something we want.

Why

The designs often ask for such a component, allthough it would be hard to display an upload progress bar (maybe on submit) it looks a lot like the original idea.

It uses a label for a drop (or click) zone to allow for custom text where the native upload button displays browser/language specific text.

How

Only if you use the boolean showFiles and if you want a list f files you also need the multiple attribute.

Checklist

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• Add or update unit tests
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Additional notes

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[dlnr]

Close PR after discussion, we'll split the file list to a separate component and add javascript listener as a code example.