Yarn complains about some deps

[marimeireles]

We should fix this:

[1/4] Resolving packages...
warning @jupyterlab/builder > @jupyterlab/buildutils > crypto@1.0.1: This package is no longer supported. It's now a built-in Node module. If you've depended on crypto, you should switch to the one that's built-in.
warning webpack > watchpack > watchpack-chokidar2 > chokidar@2.1.8: Chokidar 2 will break on node v14+. Upgrade to chokidar 3 with 15x less dependencies.
warning webpack > watchpack > watchpack-chokidar2 > chokidar > fsevents@1.2.13: fsevents 1 will break on node v14+ and could be using insecure binaries. Upgrade to fsevents 2.
warning webpack > micromatch > snapdragon > source-map-resolve > resolve-url@0.2.1: https://github.com/lydell/resolve-url#deprecated
warning webpack > micromatch > snapdragon > source-map-resolve > urix@0.1.0: Please see https://github.com/lydell/urix#deprecated
[2/4] Fetching packages...
info fsevents@2.3.2: The platform "linux" is incompatible with this module.
info "fsevents@2.3.2" is an optional dependency and failed compatibility check. Excluding it from installation.
info fsevents@1.2.13: The platform "linux" is incompatible with this module.
info "fsevents@1.2.13" is an optional dependency and failed compatibility check. Excluding it from installation.
[3/4] Linking dependencies...
warning "@jupyter-widgets/base > @lumino/coreutils@1.5.3" has unmet peer dependency "crypto@1.0.1".
[4/4] Building fresh packages...

Just adding as a reminder. I can fix this Jean-David! :)