improve spatial coverage of interactive pixel map

[wholmgren]

Would be very helpful to me if the map included Hawaii and the Caribbean.

[kandersolar]

Looks like the grid is configured to extend beyond what the map will actually show, so it might be as simple as just updating the bounds here:

unofficial-psm3-userguide/source/_static/map.js

Line 82 in b6c924b

extent: ol.proj.transformExtent([-125, -21, -66.5, 60], 'EPSG:4326', 'EPSG:3857'),

A complication: different PSM3 datasets have different extents (and potentially different grid alignments?), I'm not sure which dataset's grid that page is currently showing, and I'm not sure which one we would want it to show. User beware.