[readme] add docker tips

- covers installation using BASH_ENV

Co-authored-by: Christopher Dieringer <cdaringe@users.noreply.github.com>
Co-authored-by: Björn Holm <blollle@gmail.com>

README.md

@@ -18,6 +18,7 @@
 - [Installing and Updating](#installing-and-updating)
   - [Install & Update Script](#install--update-script)
     - [Additional Notes](#additional-notes)
+    - [Installing in Docker](#installing-in-docker)
     - [Troubleshooting on Linux](#troubleshooting-on-linux)
     - [Troubleshooting on macOS](#troubleshooting-on-macos)
     - [Ansible](#ansible)
@@ -129,6 +130,25 @@ Eg: `curl ... | NVM_DIR="path/to/nvm"`. Ensure that the `NVM_DIR` does not conta
 
 - You can instruct the installer to not edit your shell config (for example if you already get completions via a [zsh nvm plugin](https://github.com/ohmyzsh/ohmyzsh/tree/master/plugins/nvm)) by setting `PROFILE=/dev/null` before running the `install.sh` script. Here's an example one-line command to do that: `PROFILE=/dev/null bash -c 'curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.40.1/install.sh | bash'`
 
+#### Installing in Docker
+
+When invoking bash as a non-interactive shell, like in a Docker container, none of the regular profile files are sourced. In order to use `nvm`, `node`, and `npm` like normal, you can instead specify the special `BASH_ENV` variable, which bash sources when invoked non-interactively.
+
+```Dockerfile
+# Use bash for the shell
+SHELL ["/bin/bash", "-o", "pipefail", "-c"]
+
+# Create a script file sourced by both interactive and non-interactive bash shells
+ENV BASH_ENV /home/user/.bash_env
+RUN touch "${BASH_ENV}"
+RUN echo '. "${BASH_ENV}"' >> ~/.bashrc
+
+# Download and install nvm
+RUN curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.39.2/install.sh | PROFILE="${BASH_ENV}" bash
+RUN echo node > .nvmrc
+RUN nvm install
+```
+
 #### Troubleshooting on Linux
 
 On Linux, after running the install script, if you get `nvm: command not found` or see no feedback from your terminal after you type `command -v nvm`, simply close your current terminal, open a new terminal, and try verifying again.