Merge branch 'maintenance' into 'master'

ci: use node:12 as base

See merge request !56
4 jobs for master in 11 minutes and 5 seconds (queued for 2 seconds)
Status Name Job ID Coverage
  Build
passed build #57170

00:07:20

 
  Test
passed lint #57173

00:00:18

passed test:chrome #57171

00:01:41

passed test:firefox #57172

00:02:05