Switch to yarn as package manager

* yarn.lock replaces package-lock.json
* Apply prettier formatting to source files
4 jobs for devcontainer in 10 minutes (queued for 2 seconds)
Status Job ID Name Coverage
  Test
passed #217083
eslint

00:01:48

 
  Build
passed #217084
build_dev

00:08:04

 
  Deploy
passed #217170
deploy_dev

00:00:07

passed #217085
deploy_dev

00:00:05