Added button for license export

[DerBene]

Description

Add licence attestation report functionality

Addressed Issue

closes DependencyTrack/dependency-track#651

Additional Details

Added it, even though we are not 100% sure if thats the right place to put it. Documentation will be added once it's clear where the changes should be in.

Checklist

• [x] I have read and understand the contributing guidelines
• [ ] This PR introduces new or alters existing behavior, and I have updated the documentation accordingly