Add intro video

[rahulkgupta]

[vincentfretin]

3dstreet-editor.js went from 1,6M to 2,5M with the mux video player. We should probably look into lazy loading the modals again soon #557

[kfarr]

@vincentfretin agreed that would be a good thing. in addition, to lazy loading, we can reduce size with:

• removing legacy mapbox component in favor of new osm: get new osm component to work with custom tiles #787 and
• more aggressive texture compression reduce image size by 1MB #298