install error, asking for "workspaces-experimental true" in .yarnrc

[danieljsj]

I'm running docker build -t canvas-docker . per the first step in the README.

i'm getting:

error The workspace feature is currently experimental and needs to be manually enabled - please add "workspaces-experimental true" to your .yarnrc file.

I'll include a bit more context:

Step 31/40 : RUN yarn install --pure-lockfile
 ---> Running in a8e8ece83d62
yarn install v0.27.5
error The workspace feature is currently experimental and needs to be manually enabled - please add "workspaces-experimental true" to your .yarnrc file.
info Visit https://yarnpkg.com/en/docs/cli/install for documentation about this command.
The command '/bin/sh -c yarn install --pure-lockfile' returned a non-zero code: 1

Here's the full output of the command:
https://pastebin.com/raw/eVNxu9cC

I know that the yarn being used here is inside Docker, because I don't even have yarn on my local machine.

I added RUN yarn config set workspaces-experimental true to the Dockerfile, and that got me past this error -- YAY!

I'll send a pull request; you all can accept if you determine the experimental config to not pose any security risk or whatever. Thanks! (my first PR!)