added line to docs about executable=None for entrypoints

Author: tclose

docs/source/tutorial/2-advanced-execution.ipynb

@@ -345,11 +345,15 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "Of course for this to work Docker needs to work and be configured for\n",
-    "[sudo-less execution](https://docs.docker.com/engine/install/linux-postinstall/).\n",
+    "Note that for this to work Docker needs to work and be configured for\n",
+    "[sudo-less execution](https://docs.docker.com/engine/install/linux-postinstall/). If\n",
+    "the command you want to execute is the entrypoint of the container, you can set the\n",
+    "`executable` field to None, e.g.\n",
+    "`MrGrid(executable=None, in_file=nifti_file, operation=\"regrid\", voxel=(0.5, 0.5, 0.5))(environment=docker.Environment(\"mrgrid-image-with-entrypoint\"))`.\n",
     "See [Containers and Environments](../explanation/environments.rst) for more details on\n",
     "how to utilise containers and add support for other software environments.\n",
     "\n",
+    "\n",
     "It is also possible to specify functions to run at hooks that are immediately before and after\n",
     "the task is executed by passing a `pydra.engine.hooks.TaskHooks` object to the `hooks`\n",
     "keyword arg. The callable should take the `pydra.engine.job.Job` object as its only\n",