Add info about updating RAPIDS.

README.md

@@ -143,3 +143,19 @@ If this still fails, `dos2unix` can be used to change them.
 ### System has not been booted with systemd as init system (PID 1)
 
 See [the installation issue above](#Timezone-environment-variable-for-tidyverse-(relevant-for-WSL2)).
+
+## Update RAPIDS
+
+To update RAPIDS, first pull and merge [origin]( https://github.com/carissalow/rapids), such as with:
+
+```commandline
+git fetch --progress "origin" refs/heads/master
+git merge --no-ff origin/master
+```
+
+Next, update the conda and R virtual environment.
+
+```bash
+R -e 'renv::restore(repos = c(CRAN = "https://packagemanager.rstudio.com/all/__linux__/focal/latest"))'
+```
+