Add checks to avoid exporting duplicate assets

[donfour]

Is your feature request related to a problem? Please describe. Currently, we export all images and vectors, no matter if they're the same or not. For example, in this design:

We export the upper right heart icon and lower left Ethereum logo three times, which results in a lot of extra imports and props.

Describe the solution you'd like Before exporting assets, we should do a check to find duplicates.