ubuntu-dev-node12 is missing installext command

[tennox]

When I use

FROM codercom/ubuntu-dev-node12:latest
RUN installext \
    dbaeumer.vscode-eslint \
    burkeholland.simple-react-snippets

I get the error:

/bin/sh: 1: installext: not found

Basing it on codercom/ubuntu-dev:latest works fine.

Would also be great to have the source Dockerfiles in order to deploy custom ones - e.g. a ubuntu-dev-meteor image 👍

Sail version: v1.1.0
Code-Server version: 2.1692-vsc1.39.2 e14362f3224c101585a26bf7ee5fa6e3bf425046 x64