Configure JupyterLab defaults in Docker image

Disable announcements and enable line numbers for
notebooks, file editor, and console cells

Author: b3b

Dockerfile

@@ -6,7 +6,28 @@ COPY --chown=${NB_USER}:users examples /home/${NB_USER}/examples
 RUN cd /home/${NB_USER}/src && \
     python -m pip install --upgrade pip && \
     python -m pip install . --group docker && \
-    python -m pip check
+    python -m pip check && \
+    jupyter labextension disable --level=sys_prefix "@jupyterlab/apputils-extension:announcements" && \
+    mkdir -p /opt/conda/share/jupyter/lab/settings && \
+    cat > /opt/conda/share/jupyter/lab/settings/overrides.json <<'EOF'
+{
+  "@jupyterlab/notebook-extension:tracker": {
+    "codeCellConfig": {
+      "lineNumbers": true
+    }
+  },
+  "@jupyterlab/fileeditor-extension:plugin": {
+    "editorConfig": {
+      "lineNumbers": true
+    }
+  },
+  "@jupyterlab/console-extension:tracker": {
+    "promptCellConfig": {
+      "lineNumbers": true
+    }
+  }
+}
+EOF
 
 RUN cd /home/${NB_USER}/examples && \
     jupytext --to ipynb *.md && \