playground: yarn serve broken

[C Reimers]

I'm trying to get the playground up and running. I can install everything alright, but running

yarn serve

gives me:

...
Error: Cannot find module '@babel/plugin-proposal-class-properties' from '/path/to/repo/northapp-contrib'
...
code: 'MODULE_NOT_FOUND'
error Command failed with exit code 1.

I tried it with both node 12 and 13.

Do have a suggestion?

[Mads Nedergaard]

Did you run yarn install both in the root and inside the playground? :)

[C Reimers]

🛎 ding dong.