Be able to choose Dockerfile to start from instead of using dev-environments #124

Tell us about your request
First of all the Docker Dev Environments is right on target. I can't wait to see this feature expand.
One of things I think is needed is to be able to create your own base image. I've only just started using Dev Environments, so this could be my ignorance or the git repo that I started with, but when I created a dev environment from https://github.com/nestjs/typescript-starter I noticed some warnings about node version installed. The node version for the javascript was old (16.6.1 installed, the github repo wants 16.10.1).
I wanted to recreate the dockerfile used for the dev environment so I could install newer version of node, but doesn't look like I can.

Which service(s) is this request for?
Dev Environments

Tell us about the problem you're trying to solve. What are you trying to do, and why is it hard?
You'll see the issue if you create a dev environment from the github repo mentioned above.
Then start in vscode, open the terminal in vscode and do npm install

npm WARN EBADENGINE Unsupported engine {
npm WARN EBADENGINE package: '@angular-devkit/core@14.0.5',
npm WARN EBADENGINE required: {
npm WARN EBADENGINE node: '^14.15.0 || >=16.10.0',
npm WARN EBADENGINE npm: '^6.11.0 || ^7.5.6 || >=8.0.0',
npm WARN EBADENGINE yarn: '>= 1.13.0'
npm WARN EBADENGINE },
npm WARN EBADENGINE current: { node: 'v16.6.1', npm: '7.20.3' }
npm WARN EBADENGINE }
...(multiple more warnings) ...

Are you currently working around the issue?
Not sure how to work around it. I guess I could try to install newer version of node.