update readme and trigger a build

README.md

@@ -3,3 +3,24 @@
 This is the repository for the data101 datahub and local user images.
 
 See this repository's [CONTRIBUTING.md](https://github.com/berkeley-dsep-infra/data101-user-image/blob/main/CONTRIBUTING.md) for instructions. That information will eventually be migrated to docs.datahub.berkeley.edu.
+
+# building the image locally
+
+You can use [repo2-docker](https://repo2docker.readthedocs.io/en/latest/) to build and use/test the image on your own device.  
+
+launch `repo2docker` from inside the cloned image repo.  To run on a linux/WSL2 linux shell:
+```
+repo2docker . # <--- the path to the repo
+```
+
+If you are using an ARM CPU (Apple M* silicon), you will need to run `jupyter-repo2docker` with the following arguments:
+
+```
+jupyter-repo2docker --user-id=1000 --user-name=jovyan \
+  --Repo2Docker.platform=linux/amd64 \
+  --target-repo-dir=/home/jovyan/.cache \
+  -e PLAYWRIGHT_BROWSERS_PATH=/srv/conda \
+  . # <--- the path to the repo
+```
+
+If you just want to see if the image builds, but not automatically launch a notebook, then add `--no-run` to the arguments (before the final `.`).