sdmTMB 0.4.1

• Fix memory issues detected by CRAN 'Additional issues' clang-UBSAN, valgrind.

• Fix a bug predicting on new data with a specified offset and extra_time.
  #270

• Add warning around non-factor handling of the spatial_varying formula. #269

• Add experimental set_delta_model() for plotting delta models with
  ggeffects::ggpredict() (GitHub version only until next CRAN version).