Add vignette on residuals / diagnostics

[ericward-noaa]

Specifically thinking about spatial and spatial residuals and updating plots in vista. Will work on this soon. Could be standalone or folded into other vignettes

[ericward-noaa]

I went through this vignette, and think the DHARMa additions cover most of the key residual things. The plots I'd made with vista are maybe more useful at thinking about faceting diagnostics across time slices, etc -- and would blow up the vignette. Minor additions to presence - absence models here

https://github.com/pbs-assess/sdmTMB/pull/268

Thinking this can be closed