Full Outer join on Rasters

[CatchSandeepVaid]

Is your feature request related to a problem? Please describe.

Full Outer join on Rasters is not supported in geotrellis.

Describe the solution you'd like

I have 2 overlapping rasters and i want to merge them such that for overlapped section it should give me max value of the corresponding pixels.

Describe alternatives you've considered

Additional context

Add any other context or screenshots about the feature request here.